stale SigV4 headers sent unintended

Setting CURLOPTAWSSIGV4 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 is set next, leaking state information...

CVE-2026-86409

Setting CURLOPTAWSSIGV4 to NULL 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 is set next, leaking state information...

curl: CVE-2026-86409: stale SigV4 headers sent unintended

Summary Setting CURLOPTAWSSIGV4 to NULL returns CURLEOK but does not disable SigV4 authentication. The handler in lib/setopt.c clears the parameter string STRINGAWSSIGV4 but never removes the CURLAUTHAWSSIGV4 bit from data-set.httpauth. A subsequent curleasyperform on the same handle still sends ...