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Fencer Intel
medium 4.3

CVE-2026-4646 json

Insufficient input validation in GitHub plugin API causes denial of service

published 5mo ago modified 3mo ago also GHSA-rmvv-8v8w-rf7x , GO-2026-5833 , EUVD-2026-31430

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID: MMSA-2026-00638

Patch / fix

  • go github.com/mattermost/mattermost-server 10.11.15, 10.11.15+incompatible, 11.4.5, 11.4.5+incompatible, 11.5.4, 11.5.4+incompatible, 11.6.1, 11.6.1+incompatible
  • go github.com/mattermost/mattermost-plugin-github 1.0.1-0.20260330164815-c2840e980b3c
  • Mattermost Mattermost 10.11.15, 11.4.5, 11.5.4, 11.6.1, 11.7.0
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Is CVE-2026-4646 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost-server
>=11.6.0, <11.6.1
>=11.5.0, <11.5.4
>=11.4.0, <11.4.5
>=10.11.0, <10.11.15
>=10.11.0+incompatible, <10.11.15+incompatible
>=11.4.0+incompatible, <11.4.5+incompatible
>=11.5.0+incompatible, <11.5.4+incompatible
>=11.6.0+incompatible, <11.6.1+incompatible
11.6.1
11.5.4
11.4.5
10.11.15
10.11.15+incompatible
11.4.5+incompatible
11.5.4+incompatible
11.6.1+incompatible
go github.com/mattermost/mattermost-plugin-github
<1.0.1-0.20260330164815-c2840e980b3c
1.0.1-0.20260330164815-c2840e980b3c

Affected products

  • Mattermost Mattermost

Classification

Weakness
  • CWE-1287 Improper Validation of Specified Type of Input

References

Sources

Fencer Intel 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.