libexpat Project libexpat: XML External Entity (XXE) (CVE-2017-9233)
Published Last modified Sources: CVE.org, OSV
What is affected, what to do
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.
Update Python Software Foundation CPython to version 2.7.15, Python Software Foundation CPython to version 3.3.7, Python Software Foundation CPython to version 3.4.7.
- Affected
- libexpat Project libexpat
lte *..2.2.0 - Python Software Foundation CPython
lt 2.7.0..2.7.15 - Python Software Foundation CPython
lt 3.3.0..3.3.7 - Python Software Foundation CPython
lt 3.4.0..3.4.7 - Python Software Foundation CPython
lt 3.5.0..3.5.4 - Python Software Foundation CPython
lt 3.6.0..3.6.2 - Debian Linux
eq 8.0..8.0 - Debian Linux
eq 9.0..9.0 - Debian Linux
eq 10.0..10.0
- libexpat Project libexpat
- Fixed in
- Python Software Foundation CPython
2.7.15 - Python Software Foundation CPython
3.3.7 - Python Software Foundation CPython
3.4.7 - Python Software Foundation CPython
3.5.4 - Python Software Foundation CPython
3.6.2
- Python Software Foundation CPython
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Metrics
7.5
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.5
CVSS v3
Severity High on the scale from 0 to 10.
Source: CVE.org, OSV
8.7 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 95.1
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 109.90 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.5 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.5
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 8.7 %
- Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 95.1
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
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.
Source: cvelistv5, OSV (Open Source Vulnerabilities), NVD (NIST)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| libexpat_project | libexpat |
|
|
| python | python |
|
|
Vendors and products
Affected operating systems
| Linux | debian | debian_linux | 10.0 |
| Linux | debian | debian_linux | 8.0 |
| Linux | debian | debian_linux | 9.0 |
References & sources
- libexpat.github.iodoc/cve-2017-9233advisory, x_refsource_CONFIRM
- bugs.python.orgissue30694report
- github.comlibexpat/libexpat/blob/R_2_2_1/expat/Changesweb
- support.apple.comHT208144x_refsource_CONFIRM
- github.comlibexpat/libexpat/blob/master/expat/Changesx_refsource_CONFIRM
- securitytracker.com1039427Vulnerability database, x_refsource_SECTRACK
- support.apple.comHT208113x_refsource_CONFIRM
- support.apple.comHT208112x_refsource_CONFIRM
- support.apple.comHT208115x_refsource_CONFIRM
- debian.orgDSA-3898Vendor advisory, x_refsource_DEBIAN
- securityfocus.com99276Vulnerability database, x_refsource_BID
- openwall.com[oss-security] 20170618 Expat 2.2.1 security fixesMailing list, x_refsource_MLIST
- support.f5.comcsp/article/K03244804x_refsource_CONFIRM
- lists.apache.org[bookkeeper-issues] 20210628 [GitHub] [bookkeeper] padma81 opened a new issue #2746: Security Vulnerabilities in CentOS 7 image, Upgrade image to CentOS 8Mailing list, x_refsource_MLIST
- lists.apache.org[bookkeeper-issues] 20210629 [GitHub] [bookkeeper] padma81 opened a new issue #2746: Security Vulnerabilities in CentOS 7 image, Upgrade image to CentOS 8Mailing list, x_refsource_MLIST
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedMITRE
Show 37 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —http://www.debian.org/security/2017/dsa-3898Reference added —http://www.openwall.com/lists/oss-security/2017/06/17/7Reference added —http://www.securityfocus.com/bid/99276Reference added —http://www.securitytracker.com/id/1039427Reference added —https://github.com/libexpat/libexpat/blob/master/expat/ChangesReference added —https://libexpat.github.io/doc/cve-2017-9233/Reference added —https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3EReference added —https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3EReference added —https://support.apple.com/HT208112Reference added —https://support.apple.com/HT208113Reference added —https://support.apple.com/HT208115Reference added —https://support.apple.com/HT208144Reference added —https://support.f5.com/csp/article/K03244804Reference removed http://www.debian.org/security/2017/dsa-3898—Reference removed http://www.openwall.com/lists/oss-security/2017/06/17/7—Reference removed http://www.securityfocus.com/bid/99276—Reference removed http://www.securitytracker.com/id/1039427—Reference removed https://github.com/libexpat/libexpat/blob/master/expat/Changes—Reference removed https://libexpat.github.io/doc/cve-2017-9233/—Reference removed https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E—Reference removed https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E—Reference removed https://support.apple.com/HT208112—Reference removed https://support.apple.com/HT208113—Reference removed https://support.apple.com/HT208115—Reference removed https://support.apple.com/HT208144—Reference removed https://support.f5.com/csp/article/K03244804—Reference type removed http://www.debian.org/security/2017/dsa-3898 Types: Third Party Advisory—Reference type removed http://www.openwall.com/lists/oss-security/2017/06/17/7 Types: Mailing List, VDB Entry—Reference type removed http://www.securityfocus.com/bid/99276 Types: Third Party Advisory, VDB Entry—Reference type removed http://www.securitytracker.com/id/1039427 Types: Third Party Advisory, VDB Entry—Reference type removed https://github.com/libexpat/libexpat/blob/master/expat/Changes Types: Release Notes, Third Party Advisory—Reference type removed https://libexpat.github.io/doc/cve-2017-9233/ Types: Exploit, Technical Description, Vendor Advisory—Reference type removed https://support.apple.com/HT208112 Types: Third Party Advisory—Reference type removed https://support.apple.com/HT208113 Types: Third Party Advisory—Reference type removed https://support.apple.com/HT208115 Types: Third Party Advisory—Reference type removed https://support.apple.com/HT208144 Types: Third Party Advisory—Reference type removed https://support.f5.com/csp/article/K03244804 Types: Third Party Advisory—Source identifier: cve@mitre.org
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: none known, automatable: yes
Show the original change
Individual changes of this event as published by NVD Type Action Before After SSVC assessment added —{"id":"CVE-2017-9233","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-08T20:58:23.473740Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Record modifiedCVE Program
Show 37 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —http://www.debian.org/security/2017/dsa-3898Reference added —http://www.openwall.com/lists/oss-security/2017/06/17/7Reference added —http://www.securityfocus.com/bid/99276Reference added —http://www.securitytracker.com/id/1039427Reference added —https://github.com/libexpat/libexpat/blob/master/expat/ChangesReference added —https://libexpat.github.io/doc/cve-2017-9233/Reference added —https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3EReference added —https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3EReference added —https://support.apple.com/HT208112Reference added —https://support.apple.com/HT208113Reference added —https://support.apple.com/HT208115Reference added —https://support.apple.com/HT208144Reference added —https://support.f5.com/csp/article/K03244804Reference removed http://www.debian.org/security/2017/dsa-3898—Reference removed http://www.openwall.com/lists/oss-security/2017/06/17/7—Reference removed http://www.securityfocus.com/bid/99276—Reference removed http://www.securitytracker.com/id/1039427—Reference removed https://github.com/libexpat/libexpat/blob/master/expat/Changes—Reference removed https://libexpat.github.io/doc/cve-2017-9233/—Reference removed https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E—Reference removed https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E—Reference removed https://support.apple.com/HT208112—Reference removed https://support.apple.com/HT208113—Reference removed https://support.apple.com/HT208115—Reference removed https://support.apple.com/HT208144—Reference removed https://support.f5.com/csp/article/K03244804—Reference type removed http://www.debian.org/security/2017/dsa-3898 Types: Third Party Advisory—Reference type removed http://www.openwall.com/lists/oss-security/2017/06/17/7 Types: Mailing List, VDB Entry—Reference type removed http://www.securityfocus.com/bid/99276 Types: Third Party Advisory, VDB Entry—Reference type removed http://www.securitytracker.com/id/1039427 Types: Third Party Advisory, VDB Entry—Reference type removed https://github.com/libexpat/libexpat/blob/master/expat/Changes Types: Release Notes, Third Party Advisory—Reference type removed https://libexpat.github.io/doc/cve-2017-9233/ Types: Exploit, Technical Description, Vendor Advisory—Reference type removed https://support.apple.com/HT208112 Types: Third Party Advisory—Reference type removed https://support.apple.com/HT208113 Types: Third Party Advisory—Reference type removed https://support.apple.com/HT208115 Types: Third Party Advisory—Reference type removed https://support.apple.com/HT208144 Types: Third Party Advisory—Reference type removed https://support.f5.com/csp/article/K03244804 Types: Third Party Advisory—Source identifier: af854a3a-2127-422b-91ae-364da2661108
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