CVE-2026-86409

high

Description

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.

References

https://hackerone.com/reports/3973135

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-105274

https://curl.se/docs/CVE-2026-86409.json

https://curl.se/docs/CVE-2026-86409.html

Details

Source: Mitre, NVD

Published: 2026-10-20

Updated: 2026-10-29

Risk Information

CVSS v2

Base Score: 7.6

Vector: CVSS2#AV:N/AC:H/Au:N/C:C/I:C/A:C

Severity: High

CVSS v3

Base Score: 8.1

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Severity: High

EPSS

EPSS: 0.01096