CVE-2026-80255

secure cookie attribute bypass with tab

CVE-2026-80255 is fixed in 10 products on 1 platform, first by curl 8.18.0-1ubuntu2.7, released September 6, 2026. It is not reported as exploited. Patch Radar priority: High.

High

CVSS

7.5

Low

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0048

41st percentile

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.

Where it's fixed

Product	Fixed in	Fix	Released
Linux
curl · Debian 14	8.22.0-1	DEBIAN-CVE-2026-80255	Sep 19, 2026
curl · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
curl · Ubuntu 26.04.1 LTS (resolute)	8.18.0-1ubuntu2.7	curl 8.18.0-1ubuntu2.7	Sep 6, 2026
curl · sles 15.6	8.22.0-150600.4.58.1	SUSE-SU-2026:5069-1	Nov 7, 2026
curl · sles 15.7	8.22.0-150700.7.33.1	SUSE-SU-2026:5068-1	Nov 7, 2026
curl-debuginfo · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
curl-debugsource · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
libcurl · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
libcurl-debuginfo · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
libcurl-devel · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
libcurl-minimal · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
libcurl-minimal-debuginfo · Fedora 43	8.15.0-12.fc43	FEDORA-2026-D65DA12723	Nov 7, 2026
libcurl3t64-gnutls · Ubuntu 26.04.1 LTS (resolute)	8.18.0-1ubuntu2.7	libcurl3t64-gnutls 8.18.0-1ubuntu2.7	Sep 6, 2026
libcurl4t64 · Ubuntu 26.04.1 LTS (resolute)	8.18.0-1ubuntu2.7	libcurl4t64 8.18.0-1ubuntu2.7	Sep 6, 2026

Details

Published
September 6, 2026
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-80255

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