libcurl cross-origin Digest auth state leak
CVE-2026-11856 is a medium-severity vulnerability in libcurl’s HTTP Digest authentication handling. When an application successfully performs a transfer to one HTTP origin using Digest authentication and then reuses the same libcurl easy handle for a subsequent transfer to a different origin, libcurl can incorrectly carry forward and send the Authorization header state intended for the first origin to the second origin. The flaw affects libcurl versions 7.10.6 through 8.20.0 inclusive and does not affect the curl command-line tool. The issue is classified as CWE-294 because the leaked Digest authentication state can be captured by the second host and replayed against the original host for a narrowly scoped request.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Recent activity
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A curl/libcurl vulnerability involving leakage of Digest authentication state across origins.
A medium-severity curl/libcurl vulnerability that can leak Digest authentication state across origins.
A medium-severity libcurl vulnerability where reusing the same handle across different HTTP origins after Digest authentication can leak the Authorization header state to a different host, enabling replay-style impersonation for a specific request path.
A curl vulnerability involving Digest authentication state leakage across origins.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.