CVE-2026-86409 in Canonical and Haxx Products
Published on October 20, 2026
stale SigV4 headers sent unintended
Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication,
contrary to expectations and documentation. A subsequent transfer on the same
handle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL
isset next, leaking state information.
Products Associated with CVE-2026-86409
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Affected Versions
curl:- Version 8.21.0, <= 8.21.0 is affected.
- Version 8.20.0, <= 8.20.0 is affected.
- Version 8.19.0, <= 8.19.0 is affected.
- Version 8.18.0, <= 8.18.0 is affected.
- Version 8.17.0, <= 8.17.0 is affected.
- Version 8.16.0, <= 8.16.0 is affected.
- Version 8.15.0, <= 8.15.0 is affected.
- Version 8.14.1, <= 8.14.1 is affected.
- Version 8.14.0, <= 8.14.0 is affected.
- Version 8.13.0, <= 8.13.0 is affected.
- Version 8.12.1, <= 8.12.1 is affected.
- Version 8.12.0, <= 8.12.0 is affected.
- Version 8.11.1, <= 8.11.1 is affected.
- Version 8.11.0, <= 8.11.0 is affected.
- Version 8.10.1, <= 8.10.1 is affected.
- Version 8.10.0, <= 8.10.0 is affected.
- Version 8.9.1, <= 8.9.1 is affected.
- Version 8.9.0, <= 8.9.0 is affected.
- Version 8.8.0, <= 8.8.0 is affected.
- Version 8.7.1, <= 8.7.1 is affected.
- Version 8.7.0, <= 8.7.0 is affected.
- Version 8.6.0, <= 8.6.0 is affected.
- Version 8.5.0, <= 8.5.0 is affected.
- Version 8.4.0, <= 8.4.0 is affected.
- Version 8.3.0, <= 8.3.0 is affected.
- Version 8.2.1, <= 8.2.1 is affected.
- Version 8.2.0, <= 8.2.0 is affected.
- Version 8.1.2, <= 8.1.2 is affected.
- Version 8.1.1, <= 8.1.1 is affected.
- Version 8.1.0, <= 8.1.0 is affected.
- Version 8.0.1, <= 8.0.1 is affected.
- Version 8.0.0, <= 8.0.0 is affected.
- Version 7.88.1, <= 7.88.1 is affected.
- Version 7.88.0, <= 7.88.0 is affected.
- Version 7.87.0, <= 7.87.0 is affected.
- Version 7.86.0, <= 7.86.0 is affected.
- Version 7.85.0, <= 7.85.0 is affected.
- Version 7.84.0, <= 7.84.0 is affected.
- Version 7.83.1, <= 7.83.1 is affected.
- Version 7.83.0, <= 7.83.0 is affected.
- Version 7.82.0, <= 7.82.0 is affected.
- Version 7.81.0, <= 7.81.0 is affected.
- Version 7.80.0, <= 7.80.0 is affected.
- Version 7.79.1, <= 7.79.1 is affected.
- Version 7.79.0, <= 7.79.0 is affected.
- Version 7.78.0, <= 7.78.0 is affected.
- Version 7.77.0, <= 7.77.0 is affected.
- Version 7.76.1, <= 7.76.1 is affected.
- Version 7.76.0, <= 7.76.0 is affected.
- Version 7.75.0, <= 7.75.0 is affected.