CVE-2026-80255: curl — Exploit & Fix

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.

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CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0068

Probability of exploitation

0.51%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-201 CWE-201

Affected Products

Vendor	Product	Versions
haxx	curl	8.13.0 — 8.22.0

References

Advisories & Patches

https://curl.se/docs/CVE-2026-80255.html https://curl.se/docs/CVE-2026-80255.json

Exploits

https://hackerone.com/reports/3972395 https://hackerone.com/reports/3972395

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-80255? +

CVE-2026-80255 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0068, placing it in the 1th percentile for exploitation probability.

What products are affected by CVE-2026-80255? +

CVE-2026-80255 affects products from haxx, specifically: curl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-80255? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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