NULL pointer dereference in libexpat external entity parsing
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- No fix listed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-476.
Summary
libexpat through 2.9.0 is affected. A NULL pointer dereference in externalEntityInitProcessor2() mishandles empty input from an external entity subparser (CWE-476). An attacker who controls how the input stream is split into chunks can make a later parse crash the application.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
libexpat through 2.9.0 contains a NULL pointer dereference vulnerability in externalEntityInitProcessor2() in lib/xmlparse.c that mishandles the XML_TOK_NONE token from empty input. Attackers who control stream chunking can force an empty non-final first parse on an external entity subparser, causing a later parse to crash the application.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| libexpat project | libexpat | up to 2.9.0 | — | No fix listed | CNA |
- libexpat Vendorlibexpat project Affected up to 2.9.0 Fixed in — No fix listed CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:* | up to 2.9.0 | Vulnerable | libexpat project |
- cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:* Versions up to 2.9.0 Vulnerable ·libexpat project
Remediation
The sources list no fixed version for libexpat. Red Hat rates this Moderate and lists Red Hat Enterprise Linux 6 with no fix planned, and Red Hat Enterprise Linux 7, 8, 9 and 10, Red Hat Hardened Images and Red Hat OpenShift Container Platform 4 with plan none available.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet |
| Red Hat Enterprise Linux 8 | Affected | No fix yet |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
| Red Hat Hardened Images | Affected | No fix yet |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
Timeline
- 2026-10-28 Threatist record created from CVE-2026-117610
- 2026-10-28 Alias added: GHSA-v4h5-6r69-76p3
- 2026-10-28 Priority changed: MEDIUM → LOW
- 2026-11-02 CVSS score added · NVD
- 2026-11-04 Affected versions changed · Red Hat
- 2026-11-04 CVSS score added · Red Hat
- 2026-11-05 CISA SSVC decision points changed
References
More libexpat project Libexpat vulnerabilities
- TI-2022-09008 In Expat (aka libexpat) before 2.4.5, there is an integer overflow in storeRawNames. CVSS 3.1CRITICAL 9.8
- TI-2026-79488 Billion laughs detection delay in libexpat enables denial of service CVSS 4.0HIGH 8.7
- TI-2022-08947 xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert… CVSS 3.1CRITICAL 9.8
- TI-2021-20962 In Expat (aka libexpat) before 2.4.3, a left shift by 29 (or more) places in the… CVSS 3.1HIGH 8.8
- TI-2021-21076 In doProlog in xmlparse.c in Expat (aka libexpat) before 2.4.3, an integer overflow exists for m_groupSize. CVSS 3.1HIGH 8.1
- TI-2016-00645 Expat allows context-dependent attackers to cause a denial of service (crash) or possibly… CVSS 3.1CRITICAL 9.8
Sources
- CVE-2026-117610 · CVE Program
- CVE-2026-117610 · NVD
- FIRST EPSS
- GHSA-v4h5-6r69-76p3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-117610 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences