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High 8.1
local interface connection reuse mixup
When `CURLOPT_INTERFACE` (or the command line tool's `--interface` option) is set with one of the documented prefixes (`if!`, `host!`, `ifhost!`), that binding is not part of the connection reuse key, so a later transfer asking for a different source can sile…
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High 8.1
info leak uploading over WebSockets with GnuTLS
When curl is built with GnuTLS, a malicious WebSocket server can make curl send memory past its send buffer. This is due to an out of bounds read following when `gnutls_record_send()` returns a number of bytes sent **greater than the number of bytes it was gi…
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High 7.5
password leak in CURLINFO_EFFECTIVE_URL
libcurl could accidentally return a URL for `curl_easy_getinfo()`'s `CURLINFO_EFFECTIVE_URL` option containing credentials, even though neither the URL provided to libcurl nor the redirected URL did.
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High 7.5
curl_mime_free stack overflow by recursion
A deeply nested multipart MIME structure constructed via the public API causes a stack overflow in libcurl during normal cleanup operations. An excessive recursion depth within `curl_mime_free` leads to unbounded stack frame allocation during structure traver…
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High 7.5
-J no-clobber guarantee bypassed with 103 early hints
When invoked with `--remote-header-name` (`-J`), curl fails to preserve its documented anti-clobbering protection if an intermediate 103 Early Hints response precedes the final HTTP response, or if an `ETag` header is processed before `Content-Disposition` un…
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High 8.1
TFTP direction confusion
libcurl's TFTP state machine fails to validate state transitions against the requested transfer direction, accepting opening server responses for both reads and writes interchangeably. A malicious TFTP server can respond to a download request in a way that fo…
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High 8.1
never-ending loop via server response omission
By permanently omitting the final control-response line, a malicious FTP, IMAP, POP3, or SMTP server can exploit libcurl and completely bypass its configured transfer timeout mechanism, indefinitely blocking all concurrent transfers bound to the same multi-ha…
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High 8.1
server-set cookie aborts cookie jar load
When writing a long cookie name and value to a Netscape cookie jar, a remote HTTP server can make `curl` write a record that exceeds its line-length parsing limit. Consequently, any subsequent `curl` invocation reading from that same cookie jar using `--cooki…
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High 7.4
knownhost callback mismatches key as missing
When libcurl uses libssh2 with a hashed `known_hosts` file, an unrelated initial entry can cause host key validation to report a key *mismatch* as a *missing* key to the `CURLOPT_SSH_KEYFUNCTION` callback.
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High 8.1
HSTS response erases persisted entries
An authenticated HTTPS origin can supply an HSTS `max-age` value that the parser accepts, but time serialization later fails to process. On 64-bit systems, extreme max-age values compute an absolute expiry within standard time integer limits that exceeds cale…
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High 8.1
IMAP APPEND plus CRLF conversion command injection
Enabling `CURLOPT_CRLF` causes curl to advertise the raw input byte count in the `IMAP APPEND {N}` literal while transmitting line-ending expanded data. The server reads only $N$ bytes for the payload, causing the remaining overflow bytes to be interpreted an…
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High 8.1
HSTS cache import drops longer-lived child
Importing a `includeSubDomains` parent HSTS entry before a longer-lived child entry, silently drops the child. Consequently, when the parent expires, the child's valid HSTS policy is lost, causing curl to issue unencrypted HTTP requests rather than upgrading …
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High 8.1
server-set cookie erases cookie jar
A remote HTTP server can set a cookie that curl accepts and writes to a Netscape cookie jar but cannot reload. On the next invocation using the same path for `--cookie` and `--cookie-jar`, curl fails before connecting, then the cleanup procedure replaces the …
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High 8.1
redirect to SFTP or SCP bypasses host verification
A flaw in the curl command line tool's logic makes it only set SSH host verification options when interacting directly using SFTP or SCP, and not as a result of following a redirect.
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High 8.1
stale SigV4 headers sent unintended
Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL isset next, leaking sta…
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High 8.1CVE-2026-92392 Public exploit
HTTP/2 upload Use-After-Free
During an upload, curl mishandles HTTP/2 `RST_STREAM` received from the server (with reason `HTTP_1_1_REQUIRED` or `REFUSED_STREAM`) leading to a use after free of a `struct Curl_easy` object.
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High 8.2
domain-scoped PSL domain cookie
When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check when processing a `Set-Cookie` header where the `Domain` attribute explicitly matches an origin host that is itself a public suffix (e.g., `Domain=co.uk` set by `co…
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High 7.5
secure cookie attribute bypass with tab
A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on…
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High 7.5
OpenSSL pinning bypass
When `CURLOPT_PINNEDPUBLICKEY` is configured alongside options that disable standard peer verification (`CURLOPT_SSL_VERIFYPEER = 0` and `CURLOPT_SSL_VERIFYHOST = 0`), libcurl fails to enforce public key pinning on connections established without a presented …
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High 7.5
OpenSSL provider use-after-free
When performing transfers via libcurl’s multi interface, pooled TLS connections can outlive their originating easy handles. In OpenSSL 3 provider configurations, libcurl attaches an allocated library context to the easy handle's state and passes it to OpenSSL…
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High 7.4
OpenLDAP SASL authentication bypass
A flaw in the libcurl SASL negotiation for LDAP authentication allows an incomplete handshake sequence to be misinterpreted as a successful cryptographic verification. An attacker executing a Man-in-the-Middle (MITM) attack can inject a premature or shortcut …
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High 7.4
SSH improper host validation
When a libcurl-based application performs transfers via `SCP://` or `SFTP://` and utilizes the `CURLOPT_SSH_KEYFUNCTION` callback, it may silently accept an untrusted server. This vulnerability occurs when a server presents a host key type that does not match…
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High 7.5
exposing HTTP/3 early data
In this scenario, libcurl first uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate. When libcurl returns to the host…
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High 7.3
UAF after pause in socket callback
Calling `curl_easy_pause()` within the event-based `CURLMOPT_SOCKETFUNCTION` callback triggers a use-after-free vulnerability, where libcurl attempts to store a flag using a dangling struct pointer immediately after that pointer's memory has been freed.
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High 7.5CVE-2026-8932 Public exploit
incomplete mTLS config matching in conn reuse
libcurl would reuse a previously created connection even when some mTLS config related option had been changed that should have prohibited reuse. libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them m…
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High 8.1
wrong STARTTLS connection reuse
A vulnerability exists where a new transfer that uses STARTTLS to upgrade the connection might reuse an existing live connection even though the TLS configuration mismatches so it should not.
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High 7.5
proto-default skips SSH verification
When a user invokes curl using a schemeless URL combined with `--proto-default` sftp (or scp), a disconnect occurs between the tool layer and libcurl. The tool layer incorrectly infers the URL scheme, which erroneously bypasses the initialization of critical …
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High 7.5
WS Auto-PONG memory exhaustion
By default, curl automatically responds to WebSocket PING frames. Because curl lacks an upper bound on memory allocation for unacknowledged frames, a malicious server can exhaust all available memory by flooding curl with rapid, sequential PING messages.
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High 7.5
QUIC zero-length UDP datagrams busy-loop
An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server to trigger a remote denial of service against a curl or libcurl client. Because the helper function discards zero-length UDP datagrams before counting them toward the per-call packe…
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High 7.5
stale custom cookie host causes cookie leak
Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies m…
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High 7.5
wrong reuse of SMB connection
libcurl might in some circumstances reuse the wrong connection for SMB(S) transfers. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criteria mu…
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High 7.5CVE-2026-3805 Public exploit
use after free in SMB connection reuse
When doing a second SMB request to the same host again, curl would wrongly use a data pointer pointing into already freed memory.
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High 7.5
Out of bounds read for cookie path
1. A cookie is set using the `secure` keyword for `https://target` 2. curl is redirected to or otherwise made to speak with `http://target` (same hostname, but using clear text HTTP) using the same cookie set 3. The same cookie name is set - but with only a s…
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High 8.6CVE-2024-2398 EPSS 36%
HTTP/2 push headers memory-leak
When an application tells libcurl it wants to allow HTTP/2 server push, and the amount of received headers for the push surpasses the maximum allowed limit (1000), libcurl aborts the server push. When aborting, libcurl inadvertently does not free all the prev…
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High 8.8
This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy handshake. When curl is asked to pass along the h…
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High 7.5
When curl retrieves an HTTP response, it stores the incoming headers so that they can be accessed later via the libcurl…
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High 7.7
An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where it reuses a previously established SSH c…
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High 8.8
A path traversal vulnerability exists in curl <8.0.0 SFTP implementation causes the tilde (~) character to be wrongly r…
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High 7.5CVE-2022-43551 EPSS 17%
A vulnerability exists in curl <7.87.0 HSTS check that could be bypassed to trick it to keep using HTTP. Using its HSTS…
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High 8.1
curl before 7.86.0 has a double free. If curl is told to use an HTTP proxy for a transfer with a non-HTTP(S) URL, it se…