# CVE-2026-5132: Unbounded zlib decompression in Calls SDP WebSocket messages

> CVE-2026-5132: Unbounded zlib decompression in Calls SDP WebSocket messages. CVSS 6.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-5132
Last updated: 2026-10-07T15:43:56Z

- Published: 2026-09-14 10:41 UTC · Updated: 2026-10-07 15:43 UTC · Assigner: Mattermost
- CVSS: 6.5 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.42%, 36th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-409

## 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

## Affected vendors and products

- Mattermost: Mattermost

## Tracked companies

- [Mattermost](https://rewindex.com/company/mattermost.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-5132)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-5132)
- [https://mattermost.com/security-updates](https://mattermost.com/security-updates)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-5132 · Markdown: https://rewindex.com/cve/CVE-2026-5132.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-5132 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:27.068Z