LOW 3.3 Microsoft

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.

Microsoft Security Update 2023-Apr: 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.

Affected Products

References

Published: 2023-04-11 · Source: Microsoft · Feed updated: 2026-09-17
This low severity vulnerability with a CVSS score of 3.3 was published on 2023-04-11 via Microsoft. Affected: cbl2 shadow-utils 4.9-13 on CBL Mariner 2.0.
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