CVE Explorer

CVE-2026-4339

Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635

Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:cca610fac7140828a6c00ca8338509d3dd0fdb633412e474b68db84d01e58991

Known exploited

Not asserted

Disputed

Stale source

Conflicts

Affected products and versions

1 source assertion

{"defaultStatus":"unaffected","product":"Mattermost","vendor":"Mattermost","versions":[{"lessThanOrEqual":"10.11.18","status":"affected","version":"10.11.0","versionType":"semver"},{"lessThanOrEqual":"11.6.3","status":"affected","version":"11.6.0","versionType":"semver"},{"lessThanOrEqual":"11.5.6","status":"affected","version":"11.5.0","versionType":"semver"},{"status":"unaffected","version":"11.7.0"},{"status":"unaffected","version":"10.11.19"},{"status":"unaffected","version":"11.6.4"},{"status":"unaffected","version":"11.5.7"}]}

cve_program_cvelist_v5affected
urn:baitaphish:normalized-source-record:v2:f2bff7a69c1f654c117db6a8b7a119be69d7f6295dbd48c836c5695a640346b5 · sha256:3446921af776e761… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion

{"metric":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"NONE","baseScore":6.5,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N","version":"3.1"},"metric_type":"cvssV3_1"}

cve_program_cvelist_v5cvss
urn:baitaphish:normalized-source-record:v2:f2bff7a69c1f654c117db6a8b7a119be69d7f6295dbd48c836c5695a640346b5 · sha256:3446921af776e761… · /containers/cna/metrics/0/cvssV3_1

CWE assertions

1 source assertion

{"cweId":"CWE-918","description":"CWE-918: Server-Side Request Forgery (SSRF)","lang":"en","type":"CWE"}

cve_program_cvelist_v5cwe
urn:baitaphish:normalized-source-record:v2:f2bff7a69c1f654c117db6a8b7a119be69d7f6295dbd48c836c5695a640346b5 · sha256:3446921af776e761… · /containers/cna/problemTypes/0/descriptions/0

Source references

1 source assertion

{"name":"MMSA-2026-00635","tags":["vendor-advisory"],"url":"https://mattermost.com/security-updates"}

cve_program_cvelist_v5reference
urn:baitaphish:normalized-source-record:v2:f2bff7a69c1f654c117db6a8b7a119be69d7f6295dbd48c836c5695a640346b5 · sha256:3446921af776e761… · /containers/cna/references/0

Attribution and limitations

CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

← Back to CVE Explorer