---
id: CVE-2023-29383
title: >-
  In Shadow 4.13, it is possible to inject control characters into fields
  provided to the SUID program chfn (change finger)
summary: >-
  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 lis…
severity: low
cvss: 3.3
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'
cwe:
  - CWE-74
  - CWE-125
vendor: shadow_project
product: shadow
affected:
  - shadow = 4.13
published: '2023-04-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T23:17:17.783'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-29383'
references:
  - url: >-
      https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663d
    label: cve@mitre.org
  - url: 'https://github.com/shadow-maint/shadow/pull/687'
    label: cve@mitre.org
  - url: >-
      https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/
    label: cve@mitre.org
  - url: >-
      https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797
    label: cve@mitre.org
  - url: >-
      https://github.com/shadow-maint/shadow/commit/e5905c4b84d4fb90aefcd96ee618411ebfac663d
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://github.com/shadow-maint/shadow/pull/687'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2025/04/msg00026.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/cve-2023-29383-abusing-linux-chfn-to-misrepresent-etc-passwd/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=31797
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-202008.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-398330.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00425
epssPercentile: 0.35137
ingestedAt: '2026-10-15T00:02:07.132Z'
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-02-06T21:21:27.050601Z'
---

## Overview

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

- `shadow = 4.13`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.