CVE-2026-11856Haxx Curl
NVDCVSS scored by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Vulnerability Summary
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`.
(`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`.
CVSS v3.1 Base Metrics — Score 9.8 (CRITICAL)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAttack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
Affected & Patched Versions
- Haxx Curl >= 7.10.6 and < 8.21.0
- Haxx Curl 8.21.0
What to do
Prioritize this fix. Exploit code is public, so attacks can follow quickly.
- Check whether you run Haxx Curl and which version.
- Update to a patched version listed above, then confirm the new version.
- Review logs and exposed services for signs of earlier compromise.
Timeline
- Jul 3, 2026Published
- Jul 7, 2026Record last modified
Score, severity and exploitation changes are tracked from the day Watchtower started logging them.
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External References
Data last checked: Nov 15, 2026 03:31 UTC