VulnerabilityPublished 14 Apr 2023Updated 3 Nov 2025

CVE-2023-29383: shadow · Out-of-bounds Read

Affects shadowSource CVE Database V5

Not known to be exploited.

Data as of 26 Oct 2026, 17:16 UTC

Severity

Medium

Rated Medium by the CNA (mitre) · No CVSS score from NVD or the CNA

EPSS: 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Apr 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Debiandebian/shadow`pkg:deb/debian/shadow`Other threats	Affected =4.13	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should be aware of the potential for visual misrepresentation of /etc/passwd when using Shadow 4.13 and exercise caution when interpreting its contents. Monitoring for updates from the vendor is recommended.

Description

CVE-2023-29383 affects Shadow version 4.13 and involves injection of control characters into fields handled by the SUID program chfn (change finger). While direct exploitation to add new users is blocked, adversaries can manipulate the /etc/passwd file display using control characters and Unicode to create the illusion of rogue user accounts. This may lead to social-engineered denial of service by convincing administrators to take the system offline.

Impact

The vulnerability does not allow direct unauthorized user creation or system compromise. Instead, it enables an attacker to manipulate the visual representation of the /etc/passwd file, potentially misleading system administrators into believing rogue accounts exist. This could result in administrators taking the system offline unnecessarily, causing an indirect denial of service.

Summary

In Shadow 4.13, it is possible to inject control characters into fields provided to the SUID program chfn. Although direct exploitation such as adding new users is prevented by blocking certain characters like \n, adversaries can use carriage return (\r) and Unicode character manipulations to bypass restrictions on the colon character. This allows them to misrepresent the contents of /etc/passwd when viewed, potentially convincing administrators that unauthorized user accounts exist. This vulnerability does not allow direct system compromise but can be leveraged for indirect denial of service through social engineering.

CWE-125Out-of-bounds Read (opens in a new tab)
Base weaknessCWE Top 25 (2025): #8
The product reads data past the end, or before the beginning, of the intended buffer.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design · Language Selection
Use a language that provides appropriate memory abstractions.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Overread Buffers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 22:44 UTC

WeaknessesCWE-125

Technical details

References

Community reviews

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