CVE-2021-44538The olm_session_describe function in Matrix libolm before 3.2.7 is vulnerable to a buffer overflow. The Olm session object represents a…
- 9.8CriticalCVSS base score
- 2.0%Exploitation in 30 daysEPSS · top 19% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
The olm_session_describe function in Matrix libolm before 3.2.7 is vulnerable to a buffer overflow. The Olm session object represents a cryptographic channel between two parties. Therefore, its state is partially controllable by the remote party of the channel. Attackers can construct a crafted sequence of messages to manipulate the state of the receiver's session in such a way that, for some buffer sizes, a buffer overflow happens on a call to olm_session_describe. Furthermore, safe buffer sizes were undocumented. The overflow content is partially controllable by the attacker and limited to ASCII spaces and digits. The known affected products are Element Web And SchildiChat Web.
Timeline
ID reserved
By mitre
- 11 days later
· 11 days later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 2.0% · top 19% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Affected products
n/a
- affected n/a
References
References4
- https://gitlab.matrix.org/matrix-org/olm/-/tags (opens in a new tab)x_refsource_MISCx_transferred
- https://matrix.org/blog/2021/12/13/disclosure-buffer-overflow-in-libolm-and-matrix-js-sdk (opens in a new tab)x_refsource_MISCx_transferred
- DSA-5034 (opens in a new tab)vendor-advisoryx_refsource_DEBIANx_transferred
- [debian-lts-announce] 20220104 [SECURITY] [DLA 2874-1] thunderbird security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-31369 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-44538)Record last updated .