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CVE-2026-19931 is a cross-user authenticated connection-reuse vulnerability in curl and libcurl versions 7.64.1 through 8.21.0. When HTTP Negotiate authentication uses empty credentials, libcurl relies on an ambient identity supplied by SSPI or GSSAPI. The internal url_match_auth_nego() function bypasses credential comparison when conn->creds is NULL and does not detect changes to the effective ambient identity. Consequently, a request made under user B's context to the same hostname can reuse a pooled connection previously authenticated as user A, causing authentication-context confusion and potential information disclosure. curl 8.22.0 fixes the issue.
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No public exploit code observed for this vulnerability.
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16 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An authentication-related connection-reuse flaw in libcurl can send one user's request over another user's authenticated HTTP connection when Negotiate authentication and initially empty credentials are involved. The advisory rates it critical, with a CVSS v3 base score of 9.8, and reports that exploits are available. The prescribed fix is to update curl and related packages to version 1:8.22.0-1+e1 or later.
An information-disclosure vulnerability in libcurl caused by incorrect connection reuse when Negotiate authentication is used.
An HTTP connection-reuse flaw in libcurl's Negotiate authentication handling. When an initial request uses empty credentials, libcurl can incorrectly reuse a connection already authenticated as another user to the same hostname, causing a subsequent user's request to be sent over the prior user's authenticated connection.
A high-severity libcurl connection-pool authentication isolation flaw affecting Negotiate/SPNEGO authentication. In multi-user or thread-impersonation environments, a connection authenticated as one user may be assigned to another user's request, potentially causing cross-user authentication/session reuse and compromising confidentiality, integrity, and availability.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.