OESA-2026-4128

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

Security Fix(es):

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 Authorization: header field meant for hostA, to hostB.(CVE-2026-11856)

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 response that bypasses complete peer validation.(CVE-2026-13608)

A flaw in libcurl's handling of HTTP/2 Server Push streams, when the parent handle is set to share connections with other handles, can lead to use-after-free in the cleanup process.(CVE-2026-18924)

A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is done using empty credentials. This can make user B's request get sent over user A's previously authenticated connection.(CVE-2026-19931)

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 server certificate. Bypassing the pinning check under these disabled-verification conditions allows unauthenticated connections to succeed when they should be rejected.(CVE-2026-80230)

A flaw in libcurl makes it wrongly reuse an existing HTTPS connection setup for a given hostname even when using a different Native CA Store setting (CURLSSLOPT_NATIVE_CA) than when the connection was created.(CVE-2026-80231)

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.uk).

Instead of coercing it into a strict host-only cookie, libcurl saves the cookie with wildcard domain scope (.co.uk). Consequently, the cookie is inappropriately included in subsequent outbound requests or HTTP redirects to arbitrary sibling subdomains under the same public suffix (e.g., attacker.co.uk).(CVE-2026-82209)