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Fencer Intel
medium 4.3

CVE-2026-20719 json

DoS via URL Previews Rendering Malicious SVGs

published 7mo ago modified 4mo ago also GHSA-86vc-mg26-fj6x , GO-2026-5245 , EUVD-2026-15485

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits
0
none known

Summary

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to prevent rendering of external SVGs on link embeds which allows unauthenticated users to crash the Mattermost webapp and desktop app via creating an issue or PR on GitHub.. Mattermost Advisory ID: MMSA-2026-00595

Patch / fix

  • go github.com/mattermost/mattermost/server/v8 8.0.0-20260217110922-b7d4a1f1f59b, 10.11.2, 11.2.4, 11.3.2, 11.4.1
  • go github.com/mattermost/mattermost-server 10.11.2+incompatible, 11.2.4+incompatible, 11.3.2+incompatible, 11.4.1+incompatible
  • Mattermost Mattermost 10.11.12, 11.2.4, 11.3.2, 11.4.1, 11.5.0
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Is CVE-2026-20719 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
7mo ago

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% 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
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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/v8
>=11.4.0-rc1, <11.4.1
>=11.3.0-rc1, <11.3.2
>=11.2.0-rc1, <11.2.4
>=8.0.0-20260105080200-d27a2195068d, <8.0.0-20260217110922-b7d4a1f1f59b
>=10.11.0-rc1, <10.11.2
11.4.1
11.3.2
11.2.4
8.0.0-20260217110922-b7d4a1f1f59b
10.11.2
go github.com/mattermost/mattermost-server
>=10.11.0-rc1+incompatible, <10.11.2+incompatible
>=11.2.0-rc1+incompatible, <11.2.4+incompatible
>=11.3.0-rc1+incompatible, <11.3.2+incompatible
>=11.4.0-rc1+incompatible, <11.4.1+incompatible
10.11.2+incompatible
11.2.4+incompatible
11.3.2+incompatible
11.4.1+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-754 Improper Check for Unusual or Exceptional Conditions

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.