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CVE-2021-34813

30
FAUCET Score

CVE-2021-34813 is a critical stack-based buffer overflow vulnerability in Matrix libolm versions prior to 3.2.3. A malicious Matrix homeserver can exploit this flaw to crash a client attempting to retrieve an Olm encrypted room key backup, potentially leading to remote code execution in specific build configurations. With a CVSS score of 9.8 (CRITICAL), this vulnerability has a network attack vector, low attack complexity, and high impact on confidentiality, integrity, and availability. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.2.3CPE matchmatch criteria
cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
4.26%
Probability of exploitation in next 30 days
EPSS Percentile
90.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0426 is in the 83rd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

gitlab.matrix.org / matrix-org/olm/-/commit/ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b
PatchVendor Advisory
gitlab.matrix.org / matrix-org/olm/-/releases/3.2.3
Release NotesVendor Advisory
matrix.org / blog/2021/06/14/adventures-in-fuzzing-libolm
ExploitPatchVendor Advisory