curl security update
cURL is a computer software project providing a library (libcurl) and command-line tool (curl) for transferring data using various protocols.
Security Fix(es):
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_easy_cleanup(). During this final
cleanup phase, libcurl attempts to access and modify an internal structure
that was already freed during the reset operation.(CVE-2026-10536)
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 SSH security options like
CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the
libcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes
the connection via SFTP/SCP as specified. Because the tool layer skipped the
security configuration, these SSH host verification options are silently
omitted, causing curl to connect to an unverified SSH remote host without
throwing an error.(CVE-2026-12064)
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.(CVE-2026-8286)
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-party domains.(CVE-2026-8924)
When reusing a libcurl handle for sequential transfers driven by
environment-variable proxy configuration, libcurl fails to clear the proxy
authentication state between requests. Specifically, if the initial transfer
authenticates against proxyA using Digest auth, a subsequent transfer routed
through proxyB erroneously leaks the Proxy-Authorization: header intended
solely for proxyA.(CVE-2026-8927)
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 the specific key type already recorded for that host
in the known_hosts file. Instead of rejecting the mismatch, the callback
mechanism fails to properly enforce the restriction, allowing the connection
to succeed without warning and risking a potential man-in-the-middle attack.(CVE-2026-9547)
