Server-side Denial of Service while processing a specifically crafted GIF file
Priority LOW 27CWE-400Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-400.
Summary
Mattermost 6.2 and earlier fails to sufficiently process a specifically crafted GIF file when it is uploaded while drafting a post, which allows authenticated users to cause resource exhaustion while processing the file, resulting in server-side Denial of Service.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00897 59th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 6.1.1, 6.0.4, 5.39.3 +1
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | up to 6.2 | 6.1.1, 6.0.4, 5.39.3, 5.37.6 | Patch available | CNA |
- Mattermost VendorMattermost Affected up to 6.2 Fixed in 6.1.1, 6.0.4, 5.39.3, 5.37.6 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* | up to 6.2.0 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* Versions up to 6.2.0 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 6.1.1, 6.0.4, 5.39.3, 5.37.6
Timeline
- 2026-10-02 Threatist record created from CVE-2021-37865
- 2026-10-03 Alias added: GHSA-jqq9-5hrp-9jg8
References
More Mattermost vulnerabilities
- TI-2024-26695 Malicious remote can invite itself to an arbitrary local channel CVSS 3.1CRITICAL 9.6
- TI-2023-02056 Oauth authorization codes do not expire when deauthorizing an oauth2 app CVSS 3.1CRITICAL 9.1
- TI-2019-15069 An issue was discovered in Mattermost Mobile Apps before 1.26.0. CVSS 3.1CRITICAL 9.1
- TI-2024-26233 Malicious remote can add users to arbitrary teams and channels CVSS 3.1HIGH 8.7
- TI-2024-26746 Permanently local data deletion by malicious remote CVSS 3.1HIGH 8.7
- TI-2023-06508 Injection in Mattermost CVSS 3.1HIGH 8.8
Sources
- CVE-2021-37865 · CVE Program
- CVE-2021-37865 · NVD
- FIRST EPSS
- GHSA-jqq9-5hrp-9jg8 · GitHub Advisory Database · CC BY 4.0
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