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Fencer Intel
low 3.8

CVE-2026-3495 json

Unescaped variables during error page composition

published 5mo ago modified 26d ago also GHSA-jx93-pf6x-874r , GO-2026-5484 , EUVD-2026-30742

cvss
3.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to escape some variables that could contain malicious content during error page composition which allows an attacker with access to edit some site configuration to execute some malicious code via injecting some JS as part of those values.. Mattermost Advisory ID: MMSA-2026-00622

Patch / fix

  • go github.com/mattermost/mattermost/server/v8 8.0.0-20260310115442-5a1ea95044d, 10.11.14, 11.5.2
  • go github.com/mattermost/mattermost-server 5.3.2-0.20260310115442-5a1ea95044dc, 10.11.14+incompatible, 11.5.2+incompatible
  • Mattermost Mattermost 10.11.14, 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

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 3.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
NVD 3.1 4.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 3.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost/server/v8
>=10.11.0, <10.11.14
>=11.5.0, <11.5.2
<8.0.0-20260310115442-5a1ea95044d
all versions
10.11.14
11.5.2
8.0.0-20260310115442-5a1ea95044d
go github.com/mattermost/mattermost-server
<5.3.2-0.20260310115442-5a1ea95044dc
>=10.11.0+incompatible, <10.11.14+incompatible
>=11.5.0+incompatible, <11.5.2+incompatible
5.3.2-0.20260310115442-5a1ea95044dc
10.11.14+incompatible
11.5.2+incompatible
go github.com/mattermost/mattermost-server/v5
all versions
 no fix listed
go github.com/mattermost/mattermost-server/v6
all versions
 no fix listed

Affected products

  • Mattermost Mattermost

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

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.