CVE-2023-29383

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.

• CWE-74
• CWE-125

• https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663dPatch
• https://github.com/shadow-maint/shadow/pull/687Issue Tracking
• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/Exploit, Third Party Advisory
• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797Exploit, Third Party Advisory
• https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663dPatch
• https://github.com/shadow-maint/shadow/pull/687Issue Tracking
• https://lists.debian.org/debian-lts-announce/2025/04/msg00026.html
• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/Exploit, Third Party Advisory
• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797Exploit, Third Party Advisory

Published

Apr 14, 2023

Last Modified

Jun 17, 2026

Status

Modified