CVE-2026-6253

Name	CVE-2026-6253
Description	curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. while using the first proxy (using say `http://`), curl is asked to follow a redirect to a URL using another scheme (say `https://`), accessed using a second, different, proxy
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
curl (PTS)	bookworm	7.88.1-10+deb12u15	vulnerable
	bookworm (security)	7.88.1-10+deb12u5	vulnerable
	trixie	8.14.1-2+deb13u5	fixed
	forky	8.21.0-2	fixed
	sid	8.22.0-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
curl	source	trixie	8.14.1-2+deb13u4
curl	source	(unstable)	8.20.0~rc3-1

Notes

[bookworm] - curl <no-dsa> (Minor issue)
[bullseye] - curl <postponed> (Minor issue; can be fixed in next update)
https://curl.se/docs/CVE-2026-6253.html
Introduced by: https://github.com/curl/curl/commit/3b60bb725913ce7339aefef0a14b12df4c24db60 (curl-7_14_1)
Fixed by: https://github.com/curl/curl/commit/188c2f166a20fa97c2325b2da7d0e5cecc13725f (rc-8_20_0-3)