CVE-2026-4054 json
SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service
published 2026-05-15 5 mo ago modified 2026-06-25 4 mo ago also GHSA-j76w-p754-g2w7 , GO-2026-5454 , EUVD-2026-30590
- cvss
- 4.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 15%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link.. Mattermost Advisory ID: MMSA-2026-00630
Patch / fix
- go github.com/mattermost/mattermost-server 0.0.0-20260414103857-b21ef302025e, 11.4.4, 11.4.4+incompatible, 11.5.2, 11.5.2+incompatible
- Mattermost Mattermost 10.11.14, 11.4.4, 11.5.2, 11.6.0
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 5 mo ago
Exploit prediction
0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L |
| NVD | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | >=11.5.0, <11.5.2 >=0.0.0-20250731163400-5b955468ea1e, <0.0.0-20260414103857-b21ef302025e >=11.4.0, <11.4.4 >=11.4.0+incompatible, <11.4.4+incompatible >=11.5.0+incompatible, <11.5.2+incompatible |
11.5.2 0.0.0-20260414103857-b21ef302025e 11.4.4 11.4.4+incompatible 11.5.2+incompatible |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-754 Improper Check for Unusual or Exceptional Conditions
References
-
mattermost.com
/security-updates
vendor-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-4054
advisory
-
github.com
/mattermost/mattermost
package
-
github.com
/advisories/GHSA-j76w-p754-g2w7
advisory
Sources
- CVE List CVE-2026-4054
- GitHub Advisory GHSA-j76w-p754-g2w7
- NVD CVE-2026-4054
- OSV GO-2026-5454
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.