What is CVE-2017-9233?

CVE-2017-9233 is a high-severity vulnerability in Libexpat Project, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 7.5/10. Published 2017-07-25.

How severe is CVE-2017-9233?

High severity. CVSS v3 base score is 7.5 out of 10.

Is CVE-2017-9233 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

XXE in Libexpat Project

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 loop using a malformed external entity definition from an external DTD.

Vulnerability class: XXE (XML External Entity)

Published 2017-07-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.087 (95.0th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 95.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.087 · newest: 0.087 · change: 0.000

Affected products

Libexpat Project
Python
Debian Linux — versions 8.0, 9.0, 10.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

support.apple.com/HT208144 (Third Party Advisory)
libexpat.github.io/doc/cve-2017-9233/ (Vendor Advisory, Technical Description, Exploit)
github.com/libexpat/libexpat/blob/master/expat/Changes (Third Party Advisory, Release Notes)
www.securitytracker.com/id/1039427 (VDB Entry, Third Party Advisory, vdb-entry)
support.apple.com/HT208113 (Third Party Advisory)
support.apple.com/HT208112 (Third Party Advisory)
support.apple.com/HT208115 (Third Party Advisory)
www.debian.org/security/2017/dsa-3898 (vendor-advisory, Third Party Advisory)
www.securityfocus.com/bid/99276 (VDB Entry, Third Party Advisory, vdb-entry)
www.openwall.com/lists/oss-security/2017/06/17/7 (mailing-list, Mailing List, VDB Entry)

Frequently asked questions

What is CVE-2017-9233?: CVE-2017-9233 is a high-severity vulnerability in Libexpat Project, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 7.5/10. Published 2017-07-25.
How severe is CVE-2017-9233?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2017-9233 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.