Affected: AlmaLinux:9: curl, AlmaLinux:9: curl-minimal, AlmaLinux:9: libcurl, AlmaLinux:9: libcurl-devel, AlmaLinux:9: libcurl-minimal

The curl packages provide the libcurl library and the curl utility for downloading files from servers using various protocols, including HTTP, FTP, and LDAP.

Security Fix(es):

* curl: curl: Authentication bypass due to incorrect connection reuse with Negotiate authentication (CVE-2026-1965) * curl: curl: Information disclosure via OAuth2 bearer token leakage during HTTP(S) redirect (CVE-2026-3783) * curl: curl: Man-in-the-middle attack via SSH host key bypass (CVE-2026-9547) * curl: curl: Insecure connection establishment due to TLS configuration mismatch (CVE-2026-8286)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Affected: Alpaquita:25: curl, Alpaquita:stream: curl, BellSoft Hardened Containers:stream: curl

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 reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work.

An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1...

The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`.

Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLO…

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 reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work.

An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it just sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1...

The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`.

Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`,…

Affected: openEuler:20.03-LTS-SP4: curl, openEuler:22.03-LTS-SP4: curl, openEuler:24.03-LTS: curl, openEuler:24.03-LTS-SP1: curl, openEuler:24.03-LTS-SP2: curl, openEuler:24.03-LTS-SP3: curl

cURL is a computer software project providing a library (libcurl) and command-line tool (curl) for transferring data using various protocols. Security Fix(es):

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 reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work.

An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it just sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1...

The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`.

Applications can disable libcurl's reu…

curl-8.19.0-1.1 on GA media

curl: libcurl: Improper certificate validation due to cached TLS settings reuse curl: curl: Authentication bypass due to incorrect connection reuse with Negotiate authentication curl: curl: Information disclosure via OAuth2 bearer token leakage during HTTP(S) redirect curl: curl: Unauthorized access due to improper HTTP proxy connection reuse curl: curl: Insecure connection establishment due to TLS configuration mismatch curl: curl: Man-in-the-middle attack via SSH host key bypass curl: curl: SSH host verification bypass when using schemeless URLs with SFTP/SCP

Affected: Rocky Linux:9: curl

The curl packages provide the libcurl library and the curl utility for downloading files from servers using various protocols, including HTTP, FTP, and LDAP.

Security Fix(es):

* curl: curl: Authentication bypass due to incorrect connection reuse with Negotiate authentication (CVE-2026-1965)

* curl: curl: Information disclosure via OAuth2 bearer token leakage during HTTP(S) redirect (CVE-2026-3783)

* curl: curl: Man-in-the-middle attack via SSH host key bypass (CVE-2026-9547)

* curl: curl: Insecure connection establishment due to TLS configuration mismatch (CVE-2026-8286)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Security update for curl

Affected: Ubuntu:Pro:20.04:LTS: curl, Ubuntu:22.04:LTS: curl, Ubuntu:24.04:LTS: curl, Ubuntu:25.10: curl, Ubuntu:26.04:LTS: curl

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 reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work. An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1... The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`. Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLOPT_MA…

Ein Angreifer kann mehrere Schwachstellen in cURL ausnutzen, um Sicherheitsvorkehrungen zu umgehen, und um Informationen offenzulegen.