CVE-2026-85534

Name	CVE-2026-85534
Description	A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort the process or fail the HTTP/2 session.
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)
Debian Bugs	1146878

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
libsoup2.4 (PTS)	bookworm	2.74.3-1+deb12u1	fixed
	trixie	2.74.3-10.1	fixed
libsoup3 (PTS)	bookworm	3.2.3-0+deb12u2	vulnerable
	trixie	3.6.5-3	vulnerable
	forky, sid	3.6.6-1	vulnerable

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
libsoup2.4	source	(unstable)	(not affected)
libsoup3	source	(unstable)	(unfixed)			1146878

Notes

[trixie] - libsoup3 <no-dsa> (Minor issue)
[bookworm] - libsoup3 <postponed> (Minor issue)
- libsoup2.4 <not-affected> (HTTP/2 support introduced in libsoup3)
https://gitlab.gnome.org/GNOME/libsoup/-/work_items/551
https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/561