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Fencer Intel
medium 5.3

CVE-2017-18896 json

Mattermost Server allows attackers to log sensitive information via DEBUG REST API logging endpoint

published 2020-06-19 6 y ago modified 2026-06-17 4 mo ago also GHSA-63wg-qmrv-7q66 , GO-2026-4299 , EUVD-2017-9986

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 56%
public exploits
0
none known

Summary

An issue was discovered in Mattermost Server before 4.2.0, 4.1.1, and 4.0.5. It allows attackers to add DEBUG lines to the logs via a REST API version 3 logging endpoint.

Patch / fix

  • go github.com/mattermost/mattermost-server 4.0.5, 4.0.5+incompatible, 4.1.1, 4.1.1+incompatible, 4.2.0, 4.2.0+incompatible
  • mattermost mattermost_server 4.0.5, 4.1.1
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260114T191543-150000.1.137.1

suse advisories SUSE-SU-2026:0142-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Exploit prediction

0.78% chance of exploitation in the next 30 days, higher than 56% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost-server
>=4.1.0, <4.1.1
<4.0.5
>=4.2.0-rc1, <4.2.0
<4.0.5+incompatible
>=4.1.0+incompatible, <4.1.1+incompatible
>=4.2.0-rc1+incompatible, <4.2.0+incompatible
4.1.1
4.0.5
4.2.0
4.0.5+incompatible
4.1.1+incompatible
4.2.0+incompatible

Classification

Weakness
  • CWE-732 Incorrect Permission Assignment for Critical Resource

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.