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.

CVSS 3.1

3.3CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS

0.4% chance of exploitation in the next 30 days; higher than 36% of CVEs (scores of 2026-10-25)

CWEs

CWE-74, CWE-125

Published

2023-04-14

Modified

2026-10-14

Record from

the NVD, synced 2026-10-19

Affected

• shadow_project:shadow

References

• https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663d
• https://github.com/shadow-maint/shadow/pull/687
• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/
• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797
• https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663d

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