Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while…
Priority MEDIUM 49CWE-787Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-787 and the CVSS impact.
Summary
Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.
Why it matters now
EPSS 0.04262 91st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix No fix listed No fixed version in the sources yet
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:* | before 3.2.3 | Vulnerable | matrix-org |
- cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:* Versions before 3.2.3 Vulnerable ·matrix-org
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2021-34813
- 2026-10-03 Alias added: GHSA-269w-9hm6-g22q
References
More matrix-org Olm vulnerabilities
- TI-2021-20136 The olm_session_describe function in Matrix libolm before 3.2.7 is vulnerable to a buffer… CVSS 3.1CRITICAL 9.8
- TI-2024-30288 An issue was discovered in Matrix libolm through 3.2.16. CVSS 3.1MEDIUM 5.3
- TI-2024-30289 An issue was discovered in Matrix libolm through 3.2.16. CVSS 3.1MEDIUM 5.3
- TI-2024-30290 An issue was discovered in Matrix libolm through 3.2.16. CVSS 3.1MEDIUM 4.3
Sources
- CVE-2021-34813 · CVE Program
- CVE-2021-34813 · NVD
- FIRST EPSS
- GHSA-269w-9hm6-g22q · GitHub Advisory Database · CC BY 4.0
- CVE-2021-34813 · 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