Expat Out-of-Bounds Read via dtdCopy
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 fixed, 7 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-125 and the CVSS impact.
Summary
Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- 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 2.8.3 | — | No fix listed | CNA |
- libexpat Vendorlibexpat project Affected up to 2.8.3 Fixed in — No fix listed CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:* | — | — | libexpat project |
- cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:* Versions — — ·libexpat project
Remediation
Red Hat 1 advisory
- RHSA-2026:65568 Released 2026-09-08 · Red Hat rating ImportantRed Hat Hardened Images RPMs Security Update
- Red Hat Hardened Images expat-2.8.4-0.1.hum1@aarch64, expat-2.8.4-0.1.hum1@src, expat-2.8.4-0.1.hum1@x86_64 +4
Vendor assessments
Red Hat
Red Hat rating: Important. 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 OpenShift AI (RHOAI) | Affected | — |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
| Red Hat Hardened Images | Fixed | RHSA-2026:65568 |
Not affected: 1 product
- Red Hat OpenShift AI (RHOAI)
Timeline
- 2026-10-02 Threatist record created from CVE-2026-76641
- 2026-10-03 Alias added: GHSA-r6r4-8m79-7vvv
- 2026-11-06 Affected versions changed · Red Hat
References
Patch 1
Other 1
More libexpat project 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-2026-76641 · CVE Program
- CVE-2026-76641 · NVD
- FIRST EPSS
- GHSA-r6r4-8m79-7vvv · GitHub Advisory Database · CC BY 4.0
- CVE-2026-76641 · 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