curl vulnerability

A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on subsequent requests to the same host.

Published 6 Sep 2026Updated 6 Sep 20263 sources
CVSS 0.0

What happened

A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on subsequent requests to the same host.

Affected versions

curl: 8.21.0 through 8.21.0 (semver); 8.20.0 through 8.20.0 (semver); 8.19.0 through 8.19.0 (semver); 8.18.0 through 8.18.0 (semver); 8.17.0 through 8.17.0 (semver); 8.16.0 through 8.16.0 (semver); 8.15.0 through 8.15.0 (semver); 8.14.1 through 8.14.1 (semver); 8.14.0 through 8.14.0 (semver); 8.13.0 through 8.13.0 (semver) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

  • Apply vendor-provided updates or mitigations.
  • Review affected product exposure and access logs.

Public PoC references

No public PoC reference has passed the current publication threshold.