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CVE-2021-44538

31
FAUCET Score

CVE-2021-44538 is a critical buffer overflow vulnerability in the olm_session_describe function of Matrix libolm before version 3.2.7, affecting products like Element Web and SchildiChat Web. Attackers can exploit this by sending crafted messages to manipulate a receiver's session, leading to a buffer overflow with partially controllable content. With a CVSS score of 9.8, this vulnerability is highly severe, allowing for complete compromise of confidentiality, integrity, and availability without user interaction. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.9.7CPE matchmatch criteria
cpe:2.3:a:matrix:element:*:*:*:*:desktop:*:*:*
< 1.9.7CPE matchmatch criteria
cpe:2.3:a:matrix:element:*:*:*:*:web:*:*:*
>= 2.4.2, < 15.2.1CPE matchmatch criteria
cpe:2.3:a:matrix:javascript_sdk:*:*:*:*:*:*:*:*
>= 3.1.4, < 3.2.8CPE matchmatch criteria
cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:*
< 1.9.7-sc1CPE matchmatch criteria
cpe:2.3:a:schildi:schildichat:*:*:*:*:desktop:*:*:*

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
1.92%
Probability of exploitation in next 30 days
EPSS Percentile
77.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0192 is in the 66th percentile among its peer group of 36,835 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/-/tags
ProductThird Party Advisory
lists.debian.org / debian-lts-announce/2022/01/msg00001.html
Mailing ListThird Party Advisory
matrix.org / blog/2021/12/13/disclosure-buffer-overflow-in-libolm-and-matrix-js-sdk
PatchVendor Advisory
debian.org / security/2022/dsa-5034
Third Party Advisory