CVE-2026-5958

Name	CVE-2026-5958
Description	When sed is invoked with both -i (in-place edit) and --follow-symlinks, the function open_next_file() performs two separate, non-atomic filesystem operations on the same path: 1. resolves symlink to its target and stores the resolved path for determining when output is written, 2. opens the original symlink path (not the resolved one) to read the file. Between these two calls there is a race window. If an attacker atomically replaces the symlink with a different target during that window, sed will: read content from the new (attacker-chosen) symlink target and write the processed result to the path recorded in step 1. This can lead to arbitrary file overwrite with attacker-controlled content in the context of the sed process. This issue was fixed in version 4.10.
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	1134495

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
sed (PTS)	bullseye	4.7-1	vulnerable
	bookworm	4.9-1	vulnerable
	trixie	4.9-2	vulnerable
	forky, sid	4.9-3	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
sed	source	(unstable)	4.9-3			1134495

Notes

[trixie] - sed <no-dsa> (Minor issue)
[bookworm] - sed <no-dsa> (Minor issue)
[bullseye] - sed <postponed> (Minor issue; can be fixed in next update)
https://gitweb.git.savannah.gnu.org/gitweb/?p=sed.git;a=commit;h=6b9b43c55ccd3beadbc0094b983c82bdb389f33b