Description
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 products
haxx: curl
References4
- curl.se/docs/CVE-2026-80255.html PatchVendor Advisory
- curl.se/docs/CVE-2026-80255.json Vendor Advisory
- hackerone.com/reports/3972395 ExploitMitigationThird Party Advisory
- hackerone.com/reports/3972395 ExploitMitigationThird Party Advisory
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - EPSS — exploit probability
- 0% percentile: 41 · as of 3 November 2026
- CWE
- CWE-201
Could this be exploited in your environment?
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