196 results · Feed
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Critical 9.1
password leak with netrc and user in URL
When asking curl to use a `.netrc` file to find credentials and at the same time specifying a URL with a username (without a password), like `https://user@example.com/`, curl could wrongly get and use the password for *another* user set in the `.netrc` file f…
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Critical 9.8
SASL double-free
The curl logic that works with SASL authentication could end up cleaning up the GSASL context *twice* without clearing the pointer in between, making it `free()` the same pointer twice.
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Critical 9.1
trailing dot domain super cookie
A flaw in curl’s cookie parsing logic allows a malicious HTTP server to set "super cookies" that bypass the Public Suffix List check. This enables an attacker-controlled origin to inject cookies that curl subsequently scopes and transmits to unrelated third-p…
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Medium 6.5
wrong reuse for different services
libcurl might in some circumstances reuse the wrong connection when asked to do Negotiate-authenticated ones, even when they are set to use different "services". libcurl features a pool of recent connections so that subsequent requests can reuse an existing c…
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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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Critical 9.8
cross-origin Digest auth state leak
Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a different one (`hostB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Authori…
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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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Critical 9.1
Native CA trust persist
libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. An easy handle that first uses default native CA trust can continue trusting the native platform store after the application swi…
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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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Critical 9.8
HTTP/2 stream-dependency tree UAF
A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CURLOPT_STREAM_DEPENDS_E`, subsequently invokes `curl_easy_reset()`, and finally terminates the handle with `curl…
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Medium 5.3
cross-proxy Digest auth state leak
Successfully using libcurl to do a transfer over a specific HTTP proxy (`proxyA`) with **Digest** authentication and then changing the proxy host to a second one (`proxyB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Pro…
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Medium 5.3
OCSP stapling bypass with Apple SecTrust
When curl is told to use the Certificate Status Request TLS extension, often referred to as *OCSP stapling*, to verify that the server certificate is valid, it fails to detect OCSP problems and instead wrongly consider the response as fine.
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Medium 5.3
netrc credential leak with reused proxy connection
When asked to both use a `.netrc` file for credentials and to follow HTTP redirects, libcurl could leak the password used for the first host to the followed-to host under certain circumstances.
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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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Medium 5.9
proxy credentials leak over redirect-to proxy
curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the se…
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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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Medium 6.5
wrong reuse of HTTP Negotiate connection
libcurl might in some circumstances reuse the wrong connection when asked to do an authenticated HTTP(S) request after a Negotiate-authenticated one, when both use the same host. libcurl features a pool of recent connections so that subsequent requests can re…
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Medium 5.9
connection reuse ignores TLS requirement
A vulnerability exists where a connection requiring TLS incorrectly reuses an existing unencrypted connection from the same connection pool. If an initial transfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request to that same host bypasse…
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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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Medium 6.5
wrong proxy connection reuse with credentials
curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the new request uses different credentials for the HTTP proxy. The proper behavior is to create or use a separate connection.
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Medium 5.3
token leak with redirect and netrc
When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a redirect to a second URL, curl could leak that token to the second hostname under some circumstances. If the hostname that the first request is redirected to has informa…
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Medium 6.5
bad reuse of HTTP Negotiate connection
libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When …
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Medium 5.3
OpenSSL partial chain store policy bypass
When doing TLS related transfers with reused easy or multi handles and altering the `CURLSSLOPT_NO_PARTIALCHAIN` option, libcurl could accidentally reuse a CA store cached in memory for which the partial chain option was reversed. Contrary to the user's wishe…
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Medium 5.3
bearer token leak on cross-protocol redirect
When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a cross-protocol redirect to a second URL that uses an IMAP, LDAP, POP3 or SMTP scheme, curl might wrongly pass on the bearer token to the new target host.
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Medium 6.3
broken TLS options for threaded LDAPS
When doing multi-threaded LDAPS transfers (LDAP over TLS) with libcurl, changing TLS options in one thread would inadvertently change them globally and therefore possibly also affect other concurrently setup transfers. Disabling certificate verification for a…
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Medium 5.9
No QUIC certificate pinning with GnuTLS
When using `CURLOPT_PINNEDPUBLICKEY` option with libcurl or `--pinnedpubkey` with the curl tool, curl should check the public key of the server certificate to verify the peer. This check was skipped in a certain condition that would then make curl allow the c…
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Medium 4.3
missing SFTP host verification with wolfSSH
curl's code for managing SSH connections when SFTP was done using the wolfSSH powered backend was flawed and missed host verification mechanisms. This prevents curl from detecting MITM attackers and more.
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Medium 5.3
predictable WebSocket mask
curl's WebSocket code did not update the 32-bit mask pattern for each new outgoing frame as the specification says. Instead it used a fixed mask that persisted and was used throughout the entire connection. A predictable mask pattern allows for a malicious se…
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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 7.5
WebSocket endless loop
Due to a mistake in libcurl's WebSocket code, a malicious server can send a particularly crafted packet which makes libcurl get trapped in an endless busy-loop. There is no other way for the application to escape or exit this loop other than killing the threa…
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Medium 4.8CVE-2025-5025 Public exploit
No QUIC certificate pinning with wolfSSL
libcurl supports *pinning* of the server certificate public key for HTTPS transfers. Due to an omission, this check is not performed when connecting with QUIC for HTTP/3, when the TLS backend is wolfSSL. Documentation says the option works with wolfSSL, faili…
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Medium 6.5
QUIC certificate check skip with wolfSSL
libcurl accidentally skips the certificate verification for QUIC connections when connecting to a host specified as an IP address in the URL. Therefore, it does not detect impostors or man-in-the-middle attacks.
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High 7.3
gzip integer overflow
When libcurl is asked to perform automatic gzip decompression of content-encoded HTTP responses with the `CURLOPT_ACCEPT_ENCODING` option, **using zlib 1.2.0.3 or older**, an attacker-controlled integer overflow would make libcurl perform a buffer overflow.
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High 7.0
eventfd double close
libcurl would wrongly close the same eventfd file descriptor twice when taking down a connection channel after having completed a threaded name resolve.
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Low 3.4
netrc and default credential leak
When asked to use a `.netrc` file for credentials **and** to follow HTTP redirects, curl could leak the password used for the first host to the followed-to host under certain circumstances. This flaw only manifests itself if the netrc file has a `default` ent…
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Low 3.4
netrc and redirect credential leak
When asked to both use a `.netrc` file for credentials and to follow HTTP redirects, curl could leak the password used for the first host to the followed-to host under certain circumstances. This flaw only manifests itself if the netrc file has an entry that …
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Medium 5.9
HSTS subdomain overwrites parent cache entry
When curl is asked to use HSTS, the expiry time for a subdomain might overwrite a parent domain's cache entry, making it end sooner or later than otherwise intended. This affects curl using applications that enable HSTS and use URLs with the insecure `HTTP://…
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Medium 6.5
OCSP stapling bypass with GnuTLS
When curl is told to use the Certificate Status Request TLS extension, often referred to as OCSP stapling, to verify that the server certificate is valid, it might fail to detect some OCSP problems and instead wrongly consider the response as fine. If the ret…
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Medium 6.3CVE-2024-7264 EPSS 20%
ASN.1 date parser overread
libcurl's ASN1 parser code has the `GTime2str()` function, used for parsing an ASN.1 Generalized Time field. If given an syntactically incorrect field, the parser might end up using -1 for the length of the *time fraction*, leading to a `strlen()` getting per…