CVE-2026-86409

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.

Status

Awaiting Analysis - 2499f714-1537-4658-8207-48ae4bb9eae9

Published

2026-10-20

Last modified

2026-10-22

Affected products

• Curl (Curl)

References

• https://curl.se/docs/CVE-2026-86409.json
• https://curl.se/docs/CVE-2026-86409.html
• https://hackerone.com/reports/3973135