JLSEC-2026-396

When doing HTTPS transfers, libcurl might erroneously use the read callback CURLOPTREADFUNCTION to ask for data to send, even when the CURLOPTPOSTFIELDS option has been set, if the same handle previously was used to issue a PUT request which used that callback. This flaw may surprise the...

JLSEC-2026-422 When libcurl is asked to perform automatic gzip decompression of content-encoded HTTP responses with...

When libcurl is asked to perform automatic gzip decompression of content-encoded HTTP responses with the CURLOPTACCEPTENCODING option, using zlib 1.2.0.3 or older, an attacker-controlled integer overflow would make libcurl perform a buffer overflow...

JLSEC-2026-421 libcurl would wrongly close the same eventfd file descriptor twice when taking down a connection...

libcurl would wrongly close the same eventfd file descriptor twice when taking down a connection channel after having completed a threaded name resolve...

JLSEC-2026-416 When an application tells libcurl it wants to allow HTTP/2 server push, and the amount of received...

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 previously allocated headers and instead lea...

JLSEC-2026-432 libcurl accidentally skips the certificate verification for QUIC connections when connecting to a...

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...

JLSEC-2026-390

libcurl provides the CURLOPTCERTINFO option to allow applications torequest details to be returned about a server's certificate chain.Due to an erroneous function, a malicious server could make libcurl built withNSS get stuck in a never-ending busy-loop when trying to retrieve thatinformation...

JLSEC-2026-415 libcurl skips the certificate verification for a QUIC connection under certain conditions, when...

libcurl skips the certificate verification for a QUIC connection under certain conditions, when built to use wolfSSL. If told to use an unknown/bad cipher or curve, the error path accidentally skips the verification and returns OK, thus ignoring any certificate problems...

JLSEC-2026-427 When doing multi-threaded LDAPS transfers (LDAP over TLS) with libcurl, changing TLS options in one...

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 specific transfer could unintentionally...

curl: libcurl: Authentication bypass due to incorrect HTTP Negotiate connection reuse

A flaw was found in libcurl. An application using libcurl that performs an authenticated HTTPS request after a Negotiate-authenticated one to the same host may incorrectly reuse the previous connection. This authentication bypass vulnerability allows the second request to be sent over a connectio...

curl: libcurl: Credential leak via reused proxy connection during HTTP redirects

A flaw was found in libcurl. When configured to use a .netrc file for credentials and follow HTTP redirects, libcurl can inadvertently send the password from the initial connection to the redirected host. This sensitive information disclosure occurs when both the original and redirect URLs use...

curl: libcurl: Wrong file transfer due to incorrect SMB connection reuse

A flaw was found in libcurl. Due to a logical error in the connection reuse mechanism for SMB Server Message Block transfers, libcurl might reuse an existing SMB connection with a different share than intended. This vulnerability, categorized as CWE-488 Exposure of Data Element to Wrong Session,...

curl: libcurl: Information disclosure due to cookie leak when reusing connections with custom Host headers

A flaw was found in libcurl. This vulnerability allows for information disclosure when a custom Host: header is used in an initial HTTP request, and a subsequent request reuses the same connection without specifying a new Host: header. This can lead to libcurl incorrectly sending cookies intended...

libcurl 7.71.0 < 8.20.0 Cookie Leak via Stale Host Header

The version of libcurl installed on the remote host is 7.71.0 prior to 8.20.0. It is, therefore, affected by a cookie leak vulnerability: - When using the same connection handle for multiple HTTP requests, if a custom Host: header is removed in a subsequent request, the second request would use...

libcurl 7.12.0 < 8.20.0 Cross-Proxy Digest Auth State Leak

The version of libcurl installed on the remote host is 7.12.0 prior to 8.20.0. It is, therefore, affected by a cross-proxy digest auth state leak vulnerability: - libcurl improperly handles Digest authentication headers when reusing handles across different HTTP proxies. When a client switches fr...

libcurl 7.14.0 < 8.20.0 Netrc Password Leak on HTTP Redirect

The version of libcurl installed on the remote host is 7.14.0 prior to 8.20.0. It is, therefore, affected by a netrc password leak vulnerability: - 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...

CVE-2026-6276

A flaw was found in libcurl. This vulnerability allows for information disclosure when a custom Host: header is used in an initial HTTP request, and a subsequent request reuses the same connection without specifying a new Host: header. This can lead to libcurl incorrectly sending cookies intended...

CVE-2026-6429

A flaw was found in libcurl. When configured to use a .netrc file for credentials and follow HTTP redirects, libcurl can inadvertently send the password from the initial connection to the redirected host. This sensitive information disclosure occurs when both the original and redirect URLs use...

CVE-2026-5773

A flaw was found in libcurl. Due to a logical error in the connection reuse mechanism for SMB Server Message Block transfers, libcurl might reuse an existing SMB connection with a different share than intended. This vulnerability, categorized as CWE-488 Exposure of Data Element to Wrong Session,...

CVE-2026-5545

A flaw was found in libcurl. An application using libcurl that performs an authenticated HTTPS request after a Negotiate-authenticated one to the same host may incorrectly reuse the previous connection. This authentication bypass vulnerability allows the second request to be sent over a connectio...

UBUNTU-CVE-2026-5773

libcurl might in some circumstances reuse the wrong connection for SMBS 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 must be met. Due to a logical error in the...