Weakness (CWE)
CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers
The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.
More detail
HTTP agents or components may include a web server, load balancer, reverse proxy, web caching proxy, application firewall, web browser, etc. Regardless of the role, they are expected to maintain coherent, consistent HTTP communication state across all components. However, including unexpected data in an HTTP header allows an attacker to specify the entirety of the HTTP message that is rendered by the client HTTP agent (e.g., web browser) or back-end HTTP agent (e.g., web server), whether the message is part of a request or a response.
When an HTTP request contains unexpected CR and LF characters, the server may respond with an output stream that is interpreted as "splitting" the stream into two different HTTP messages instead of one. CR is carriage return, also given by %0d or \r, and LF is line feed, also given by %0a or \n.
In addition to CR and LF characters, other valid/RFC compliant special characters and unique character encodings can be utilized, such as HT (horizontal tab, also given by %09 or \t) and SP (space, also given as + sign or %20).
These types of unvalidated and unexpected data in HTTP message headers allow an attacker to control the second "split" message to mount attacks such as server-side request forgery, cross-site scripting, and cache poisoning attacks.
How to prevent it (4 mitigations)
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Implementation
Construct HTTP headers very carefully, avoiding the use of non-validated input data.
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Implementation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. If an input does not strictly conform to specifications, reject it or transform it into something that conforms.
When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
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Implementation
Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
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Implementation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Source: MITRE CWE-113
127 results · Feed
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Medium 6.5
HCL AION is affected by multiple security vulnerabilities.
HCL AION is affected by a vulnerability where user-controlled input could be included in HTTP response headers without proper neutralization of CR/LF characters. This may allow an attacker to inject headers or split responses, potentially resulting in uninten…
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Critical 10.0
Apache Juneau: Response header CRLF injection and open redirect when applications set headers or redirect targets from request data
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability in Apache Juneau. The Apache Juneau REST server passed response header values and redirect targets to the servlet container unchecked. An application that sets…
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Medium 4.3
Multiple vulnerabilities that affects IBM Db2 Genius Hub
IBM Db2 Genius Hub 1.1.2, 1.1.3, 1.1.4, 1.1.5 could allow a remote authenticated attacker to conduct HTTP response splitting due to improper neutralization of HTTP headers.
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High 7.2
CGI versions before 5.00 for Perl allow HTTP header injection via entity decoding after the newline check in header and unchecked values in multipart_start and do_push
CGI versions before 5.00 for Perl allow HTTP header injection via entity decoding after the newline check in header and unchecked values in multipart_start and do_push. With autoEscape off, header decodes HTML entities in extra header values after its newline…
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High 8.2
AdminNeo has Cookie Attribute Injection via Unsanitized X-Forwarded-Prefix in Set-Cookie Headers
### Summary AdminNeo versions 4.6.0 through at least 5.5.0 are vulnerable to cookie attribute injection via the `X-Forwarded-Prefix` HTTP header. An attacker who can influence this header (e.g., through a reverse proxy that forwards it from clients, an attack…
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Low 2.1
CRLF injection in Proxy-Authorization header built from proxy_auth_fun in hackney
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in hackney_http_connect in benoitc hackney allows HTTP Request Splitting via the value a proxy_auth_fun callback returns. After a 407 response from an …
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Critical 9.3
Goobi viewer: IIIF Auth 2.0 origin parameter unsanitized — CSP malformation and reflected XSS
The Goobi viewer is a web application that allows digitised material to be displayed in a web browser. From version 25.08 to before version 26.05, the IIIF Auth 2.0 endpoints auth/login and auth/token in AuthorizationFlowResource accept an origin query parame…
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Low 3.7
cpp-httplib open_stream serializes CRLF in request target into HTTP request line
cpp-httplib is a C++ header-only HTTP/HTTPS library. From 0.29.0 until 0.51.0, Client::open_stream in httplib.h accepts a caller-controlled path that reaches detail::write_request_line() without the detail::encode_path() protection used by the ordinary buffer…
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Medium 5.4
HTTP response splitting in Progress MarkLogic Server Query Console
Progress MarkLogic Server 12.x releases before 12.1.0 and 11.x releases before 11.3.7 do not sufficiently sanitize input used by the Query Console file-exploration endpoint, which could allow HTTP response splitting and unintended client-side response handlin…
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Critical 9.2
An HTTP header injection vulnerability was found in the ADM
An HTTP header injection vulnerability in start-page-loader.cgi of ADM allows an unauthenticated remote attacker to read arbitrary files on the host system. By sending a crafted HTTP request with injected headers via the state parameter, the attacker can leve…
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High 8.4
MISP sachertortephp - CakeResponse::download() HTTP Response Splitting via Unsanitized Filename Enables Stored XSS
The CakeResponse::download() method in lib/Cake/Network/CakeResponse.php constructs a Content-Disposition header by directly interpolating a caller-supplied filename into a quoted-string value without sanitization. Two distinct injection vectors exist in the …
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Medium 6.5
Dancer2 versions before 2.2.0 for Perl do not strip CR and LF from response header names in headers_to_array
Dancer2 versions before 2.2.0 for Perl do not strip CR and LF from response header names in headers_to_array. The routine removes CR and LF from each header value but not from the name. A name carrying them therefore reaches the PSGI server intact. A server t…
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Medium 4.3
ST Engineering iDirect iDX/Evo iDX HTTP Request authorize response splitting
A vulnerability was determined in ST Engineering iDirect iDX and Evo iDX. This vulnerability affects unknown code of the file /authorize of the component HTTP Request Handler. Executing a manipulation of the argument Success can lead to http response splittin…
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High 8.2
Sanic: HTTP response header injection via missing CR/LF validation in Sanic HTTP/1.1 responses
Sanic is an opensource python web server/framework. Prior to version 24.12.1, and in version 25.12.0, the HTTP/1.1 response pipeline in sanic/response/types.py serializes response header names and values without rejecting carriage-return or line-feed characte…
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Medium 6.3
oRPC: Vary Header Injection in CORS Plugin leading to potential Cache/CORS Bypass
oRPC is an tool that helps build APIs that are end-to-end type-safe and adhere to OpenAPI standards. Prior to 1.14.8, the @orpc/server CORS plugin in packages/server/src/plugins/cors.ts copies a client's incoming Vary request header into the response instead …
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Medium 4.8
Http4s: Set-Cookie rendering does not escape attribute delimiters
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, ResponseCookie.render writes attacker-influenced name, content, domain, path, and extension values without neutralizing semicolons or control characters. An application that constr…
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Medium 5.4
Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs
Tornado before 6.5.8 contains an incomplete fix for cookie attribute injection that allows attackers to inject arbitrary cookie attributes by passing capitalized or legacy keyword arguments to set_cookie. Attackers can embed semicolon-delimited data in capita…
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Medium 5.4
Tornado before 6.4.1 CRLF Injection via CurlAsyncHTTPClient
Tornado before 6.4.1 contains a CRLF injection vulnerability in CurlAsyncHTTPClient that fails to reject carriage return and line feed characters in request headers. Attackers can inject CRLF sequences into header values to inject arbitrary headers or constru…
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High 7.3
a2aproject a2a-java Authorization Header Construction BasePushNotificationSender.java BasePushNotificationSender.dispatchNotification response splitting
A weakness has been identified in a2aproject a2a-java 1.2.0. The affected element is the function BasePushNotificationSender.dispatchNotification of the file server-common/src/main/java/org/a2aproject/sdk/server/tasks/BasePushNotificationSender.java of the co…
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Medium 5.4
Ajaxify Comments < 3.2 - Unauthenticated HTTP Header Injection
The Ajaxify Comments WordPress plugin before 3.2 is vulnerable to HTTP Header Injection due to insufficient input sanitization and output escaping on user-supplied data. This makes it possible for unauthenticated attackers to inject arbitrary HTTP headers.
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Medium 5.3
cpp-httplib: CRLF injection via unvalidated HTTP trailer headers in chunked response writing
cpp-httplib is a C++ header-only HTTP/HTTPS library. In version 0.49.0, the chunked-response trailer output path writes trailer header names and values directly to the socket without validating them, allowing CRLF sequences in a trailer field to inject additi…
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Low 3.7
Spring Framework response splitting in ContentDisposition
Applications that build a Content-Disposition header value from untrusted input may be vulnerable to HTTP response splitting when the input is a malicious file name. Spring Framework 7.0.0 - 7.0.8 Spring Framework 6.2.0 - 6.2.19 Spring Framework 6.1.0 - 6.1.2…
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High 8.8
go-wind-cms (GoWind) before 1.0.0 has a missing authorization vulnerability. The NewAuthorizer() function in app/admin/…
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High 8.1
TIM Flow < 26.0.6 CRLF Injection via rt Parameter
TIM Flow before 26.0.6 contains a CRLF injection vulnerability that allows remote attackers to inject arbitrary HTTP headers and response body content by embedding unsanitized carriage return and line feed sequences in the rt URL parameter, which is reflected…
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Medium 6.8
ePA 3.x Integration: HTTP Header Injection in VAU Inner Requests
ePA 3.x Integration implements the authorization workflow and writes Medical Information Objects to Germany's electronic patient record. Prior to 1.3.0, ePA 3.x Integration does not neutralize CRLF characters in values used by app/vau/VAUProtokoll.py to const…
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Critical 9.8
FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection
FreeRDP before 3.29.0 (affected versions <= 3.28.0) does not validate CRLF and control characters in the server-controlled RDP redirection TargetNetAddress field. This value is copied into the client's ServerHostname and, when the client connects through an H…
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Medium 5.4CVE-2026-66746 Public exploit
Rouille 0.4.0 - 3.6.2 HTTP Response Splitting via Header Injection
Rouille 0.4.0 through 3.6.2 contains an HTTP response splitting vulnerability that allows remote attackers to inject arbitrary response headers by embedding carriage return (0x0D) or line feed (0x0A) bytes into attacker-controlled input. Attackers can exploit…
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Low 3.7CVE-2026-66753 Public exploit
tiny-http 0.12.0 HTTP Response Splitting via Header Injection
tiny-http through 0.12.0 contains an HTTP header injection vulnerability that allows attackers to inject carriage return (0x0D) and line feed (0x0A) bytes into HTTP header values on both request and response sides due to insufficient validation in header pars…
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Medium 5.3
swift-nio-http2: Missing CR/LF/NUL validation in header values
SwiftNIO HTTP/2 was missing validation on inbound HEADERS frames that let CR, LF, NUL, SP and other control characters reach an HTTP/1.1 backend through NIOHTTP2's HTTP/2-to-HTTP/1 codec, enabling HTTP request smuggling or response splitting. This vulnerabili…
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High 7.1
Adminer < 5.4.3 Cookie Injection via X-Forwarded-Prefix Header
Adminer before 5.4.3 contains a cookie injection vulnerability that allows attackers to manipulate cookie attributes by injecting arbitrary values through the unsanitized X-Forwarded-Prefix HTTP header used in Set-Cookie path attributes. Attackers can exploit…
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Medium 4.7
secure_headers: CSP directive injection via sandbox, plugin_types, and report_to when given untrusted input
secure_headers manages application of security headers with many safe defaults. Prior to 7.3.0, secure_headers builds the Content-Security-Policy value by stitching directives with ; separators, and build_sandbox_list_directive, build_media_type_list_directiv…
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Low 3.1
An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability [CWE-113] vulner…
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Low 3.4
An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability [CWE-113] vulner…
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Medium 6.9
Kirby: Request header injection in `Http\Remote`
Kirby is an open-source content management system. Prior to 4.9.4 and 5.4.4, Kirby sites and plugins using the Kirby Http Remote class, including Remote::request(), Remote::get(), and Remote::post(), to send outgoing HTTP requests with untrusted data in the h…
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Medium 6.5
Hono - Vary Header Injection in CORS Middleware
Hono before 4.10.3 contains a flaw in its CORS middleware: when the origin is not set to "*", the middleware copies the Vary header from the incoming request into the response. Because Vary is a response header that should be managed by the server, an attacke…
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Medium 4.8
guzzlehttp/psr7: CRLF Injection in HTTP Start-Line Serialization
guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Prior to 2.12.1, guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an appl…
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Medium 5.3
Hono - Missing Cookie Name Validation in setCookie()
Hono before 4.12.12 does not validate cookie names on the write path in the setCookie(), serialize(), and serializeSigned() functions, allowing invalid characters such as control characters (e.g. \r or \n) when an application passes a user-controlled cookie n…
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Low 2.7
AIOHTTP: CRLF injection in multipart headers
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.0, attacker-controlled input included into multipart/payload headers can be used to modify a request to inject additional headers or similar. In the unlikely situati…
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Medium 6.5
Apache CXF: OAuth2: HTTP Response Splitting via WWW-Authenticate Realm Injection
A CRLF injection vulnerability exists in the OAuth2 AuthorizationUtils class. When constructing the WWW-Authenticate response header, the 'realm' parameter is concatenated without sanitizing Carriage Return (CR) and Line Feed (LF) characters. If an attacker c…
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Low 3.7
Axios: Proxy-Authorization Header Injection via Prototype Pollution — Incomplete Null-Prototype Fix
Axios is a promise based HTTP client for the browser and Node.js. From 1.15.2 to before 1.16.0, nested objects created by utils.merge() (e.g., config.proxy) are still constructed as plain {} with Object.prototype in their chain. The setProxy() function at lib…