CVE-2023-29383

Name	CVE-2023-29383
Description	In Shadow 4.13, it is possible to inject control characters into fields provided to the SUID program chfn (change finger). Although it is not possible to exploit this directly (e.g., adding a new user fails because \n is in the block list), it is possible to misrepresent the /etc/passwd file when viewed. Use of \r manipulations and Unicode characters to work around blocking of the : character make it possible to give the impression that a new user has been added. In other words, an adversary may be able to convince a system administrator to take the system offline (an indirect, social-engineered denial of service) by demonstrating that "cat /etc/passwd" shows a rogue user account.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1034482

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
shadow (PTS)	bullseye	1:4.8.1-1	vulnerable
	bookworm	1:4.13+dfsg1-1	vulnerable
	sid, trixie	1:4.16.0-7	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
shadow	source	(unstable)	1:4.13+dfsg1-2			1034482

Notes

[bookworm] - shadow <no-dsa> (Minor issue)
[bullseye] - shadow <no-dsa> (Minor issue)
[buster] - shadow <no-dsa> (Minor issue)
https://github.com/shadow-maint/shadow/pull/687
Fixed by: https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663d (4.14.0-rc1)
Regression fix: https://github.com/shadow-maint/shadow/commit/2eaea70111f65b16d55998386e4ceb4273c19eb4 (4.14.0-rc1)
https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797
https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/