Buffer overflow in Matrix Olm
CVE-2021-34813
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.043 (90.7th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 91st percentile — 90.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.043 · newest: 0.043 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- matrix.org/blog/2021/06/14/adventures-in-fuzzing-libolm (Exploit, Patch, Vendor Advisory)
- gitlab.matrix.org/matrix-org/olm/-/releases/3.2.3 (Release Notes, Vendor Advisory)
- gitlab.matrix.org/matrix-org/olm/-/commit/ccc0d122ee1b4d5e5ca4ec1432086be17d5f9… (Patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2021-34813?
- CVE-2021-34813 is a critical-severity vulnerability in Matrix Olm, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-06-16.
- How severe is CVE-2021-34813?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2021-34813 known to be exploited?
- 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.