CVE-2026-5132
Unbounded zlib decompression in Calls SDP WebSocket messages
- Published
- Updated
- Reserved
- Assigned by
- Mattermost
Description
Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to limit size of unpacked SDP messages compressed with zlib, which allows attacker to deny service or crash server via sending many SDP messages that unpack to large size.. Mattermost Advisory ID: MMSA-2026-00643
Timeline
ID reserved
By Mattermost
- 6 months later
· 6 months later
Published
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 |
|---|---|---|---|
| MattermostCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.42% · top 63% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Weakness
Affected products
- affected 11.9.0 – ≤ 11.9.0
- affected 11.8.0 – ≤ 11.8.4
- affected 11.7.0 – ≤ 11.7.7
- affected 10.11.0 – ≤ 10.11.22
- unaffected 11.10.0
- unaffected 11.9.1
- unaffected 11.8.5
- unaffected 11.7.8
- unaffected 10.11.23
What to do
Solution: Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 or higher.
References (1)
- MMSA-2026-00643 (opens in a new tab)vendor-advisory
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)
- 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://trackcve.app/cve/CVE-2026-5132)Record last updated .