What is CVE-2026-80255?

CVE-2026-80255 is a high-severity vulnerability in Curl, classified under Insertion of Sensitive Information into Sent Data. CVSS score: 7.5/10. Published 2026-09-06.

How severe is CVE-2026-80255?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Curl

CVE-2026-80255

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 2026-09-06 · last modified 2026-09-15.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.005 (40.3th percentile), scored 2026-10-22.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.005 · change: -0.002

Affected products

Curl — versions 8.14.0, 8.18.0, 8.15.0
Haxx Curl

Weakness classification (CWE)

CWE-201 — Insertion of Sensitive Information into Sent Data

References

2499f714-1537-4658-8207-48ae4bb9eae9 (Vendor Advisory)
2499f714-1537-4658-8207-48ae4bb9eae9 (Patch, Vendor Advisory)
2499f714-1537-4658-8207-48ae4bb9eae9 (Exploit, Third Party Advisory, Mitigation)

Frequently asked questions

What is CVE-2026-80255?: CVE-2026-80255 is a high-severity vulnerability in Curl, classified under Insertion of Sensitive Information into Sent Data. CVSS score: 7.5/10. Published 2026-09-06.
How severe is CVE-2026-80255?: High severity. CVSS v3 base score is 7.5 out of 10.