CVE-2023-29383

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CVE-2023-29383

Summary:

Details: 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.

References: https://lists.debian.org/debian-lts-announce/2025/04/msg00026.html, https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/29xxx/CVE-2023-29383.json, https://nvd.nist.gov/vuln/detail/CVE-2023-29383, https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797, 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/