Unbounded zlib decompression in Calls SDP WebSocket messages
Summary
| CVE | CVE-2026-5132 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-14 11:17:04 UTC |
| Updated | 2026-10-07 15:43:56 UTC |
| 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 |
Risk And Classification
Primary CVSS: v3.1 6.5 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.002350000 probability, percentile 0.145540000 (date 2026-09-16)
Problem Types: CWE-409 | CWE-409 CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Mattermost | Mattermost Server | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 11.9.0 11.9.0 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.8.0 11.8.4 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.7.0 11.7.7 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 10.11.0 10.11.22 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.10.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.9.1 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.8.5 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.7.8 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 10.11.23 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: daw10 (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 or higher.
There are currently no legacy QID mappings associated with this CVE.