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Fencer Vulns
medium 5.3

CVE-2026-2456 json

Denial of Service via Unbounded Memory Allocation in Integration Actions

published 2026-03-16 7 mo ago modified 2026-06-17 4 mo ago also GHSA-34g8-9fpp-46ch , GO-2026-4726 , EUVD-2026-12383

cvss
5.3
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 6%
public exploits
0
none known

Summary

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 Mattermost fails to limit the size of responses from integration action endpoints, which allows an authenticated attacker to cause server memory exhaustion and denial of service via a malicious integration server that returns an arbitrarily large response when a user clicks an interactive message button.. Mattermost Advisory ID: MMSA-2026-00571

Patch / fix

  • go github.com/mattermost/mattermost/server/v8 8.0.0-20260127165411-fe3052073dc6
  • go github.com/mattermost/mattermost-server 5.3.2-0.20260127165411-fe3052073dc6, 10.11.11, 10.11.11+incompatible, 11.2.3, 11.2.3+incompatible, 11.3.1, 11.3.1+incompatible
  • Mattermost Mattermost 10.11.11, 11.2.3, 11.3.1, 11.4.0
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260326T203309-150000.1.155.2

suse advisories SUSE-SU-2026:1135-1

  • 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
7 mo ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 3.1 5.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost/server/v8
<8.0.0-20260127165411-fe3052073dc6
8.0.0-20260127165411-fe3052073dc6
go github.com/mattermost/mattermost-server
<5.3.2-0.20260127165411-fe3052073dc6
>=10.11.0-rc1, <10.11.11
>=11.2.0-rc1, <11.2.3
>=11.3.0-rc1, <11.3.1
>=10.11.0-rc1+incompatible, <10.11.11+incompatible
>=11.2.0-rc1+incompatible, <11.2.3+incompatible
>=11.3.0-rc1+incompatible, <11.3.1+incompatible
5.3.2-0.20260127165411-fe3052073dc6
10.11.11
11.2.3
11.3.1
10.11.11+incompatible
11.2.3+incompatible
11.3.1+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-789 Memory Allocation with Excessive Size Value

References

Sources

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.