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
CVE-2026-3495
Score 3.8 from GitHub Security Advisory (severity: LOW) published 2026-05-18. NVD baseline CVSS 3.8; sources differ by 0.0.
- Lower severity and no public exploit yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 3.8
- EG Score
- 3.8(medium)
- EPSS
- 4.0%
- KEV
- Not listed
Published
May 18, 2026
Last Modified
May 19, 2026
References (1)
- responsibledisclosure@mattermosthttps://mattermost.com/security-updates
Vendor Advisories for CVE-2026-3495(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(2 across 1 ecosystem)
Go(2)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| github.com/mattermost/mattermost-server | — | 5.3.2-0.20260310115442-5a1ea95044dc | — |
| github.com/mattermost/mattermost/server/v8 | — | 8.0.0-20260310115442-5a1ea95044d | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 6× in last 7d / 36× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-11 08:27 UTCEPSS rescore
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- 2026-06-19 19:25 UTCEPSS rescore
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- 2026-06-17 13:17 UTCEG score recompute
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- 2026-06-07 16:51 UTCEG score recompute
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- 2026-06-04 11:05 UTCEG score recompute
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- 2026-06-01 05:19 UTCEG score recompute
- 2026-06-01 05:19 UTCGHSA enrichment
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- 2026-05-20 22:38 UTCEPSS rescore
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- 2026-05-20 11:51 UTCEG score recompute
- 2026-05-20 11:51 UTCGHSA enrichment
- 2026-05-20 11:22 UTCEPSS rescore
- 2026-05-20 11:22 UTCEPSS rescore
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Frequently asked(5)
What is CVE-2026-3495?
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Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-3495
Is Your Infrastructure Affected by CVE-2026-3495?
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