CVE-2026-42505

Name	CVE-2026-42505
Description	Handshakes which used Encrypted Client Hello could be de-anonymized by a passive network observer due to a disclosure of pre-shared key identities in the unencrypted client hello.
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
golang-1.15 (PTS)	bullseye	1.15.15-1~deb11u4	fixed
golang-1.19 (PTS)	bookworm	1.19.8-2	fixed
golang-1.24 (PTS)	trixie	1.24.4-1	vulnerable
golang-1.25 (PTS)	forky, sid	1.25.12-1	fixed
golang-1.26 (PTS)	forky, sid	1.26.5-1	fixed
golang-1.27 (PTS)	forky, sid	1.27~rc2-1	fixed

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

Package	Type	Release	Fixed Version
golang-1.15	source	(unstable)	(not affected)
golang-1.19	source	bookworm	(not affected)
golang-1.19	source	(unstable)	(unfixed)
golang-1.24	source	(unstable)	(unfixed)
golang-1.25	source	(unstable)	1.25.12-1
golang-1.26	source	(unstable)	1.26.5-1
golang-1.27	source	(unstable)	1.27~rc2-1

Notes

[trixie] - golang-1.24 <no-dsa> (Minor issue)
[bookworm] - golang-1.19 <not-affected> (crypto/tls client ECH introduced in Go 1.23; absent in 1.19)
- golang-1.15 <not-affected> (Vulnerable code introduced later)
crypto/tls client Encrypted Client Hello introduced in Go 1.23 (issue #63369)
https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc
https://github.com/golang/go/issues/79282
Fixed by: https://github.com/golang/go/commit/ca8ca590ccfda1e1c3186faf975afdb02cb6d2f0 (go1.26.5)
Fixed by: https://github.com/golang/go/commit/fc9f821bb660c1dcb9e57868b62f62bf3afb5842 (go1.25.12)