CVE-2026-95666 (GCVE-0-2026-95666)
Vulnerability from cvelistv5 – Published: 2026-09-22 13:11 – Updated: 2026-09-22 13:57
VLAI
EPSS
VEX
Title
Unbounded post ID array in the bulk reactions endpoint allows denial of service
Summary
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771
Severity
4.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-22 13:55 UTC
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.9.0 , ≤ 11.9.1
(semver)
Affected: 11.8.0 , ≤ 11.8.5 (semver) Affected: 11.7.0 , ≤ 11.7.10 (semver) Affected: 11.10.0 , ≤ 11.10.1 (semver) Unaffected: 11.11.0 Unaffected: 11.9.2 Unaffected: 11.8.6 Unaffected: 11.7.11 Unaffected: 11.10.2 |
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-95666",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-22T13:55:15.216071Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-22T13:57:00.428Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Mattermost",
"vendor": "Mattermost",
"versions": [
{
"lessThanOrEqual": "11.9.1",
"status": "affected",
"version": "11.9.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.8.5",
"status": "affected",
"version": "11.8.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.7.10",
"status": "affected",
"version": "11.7.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.10.1",
"status": "affected",
"version": "11.10.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "11.11.0"
},
{
"status": "unaffected",
"version": "11.9.2"
},
{
"status": "unaffected",
"version": "11.8.6"
},
{
"status": "unaffected",
"version": "11.7.11"
},
{
"status": "unaffected",
"version": "11.10.2"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "idr"
}
],
"descriptions": [
{
"lang": "en",
"value": "Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771"
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 4.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770: Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-22T13:11:13.798Z",
"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
"shortName": "Mattermost"
},
"references": [
{
"name": "MMSA-2026-00771",
"tags": [
"vendor-advisory"
],
"url": "https://mattermost.com/security-updates"
}
],
"solutions": [
{
"lang": "en",
"value": "Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher."
}
],
"source": {
"advisory": "MMSA-2026-00771",
"defect": [
"https://mattermost.atlassian.net/browse/MM-70177"
],
"discovery": "EXTERNAL"
},
"title": "Unbounded post ID array in the bulk reactions endpoint allows denial of service",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
"assignerShortName": "Mattermost",
"cveId": "CVE-2026-95666",
"datePublished": "2026-09-22T13:11:13.798Z",
"dateReserved": "2026-09-22T13:09:02.237Z",
"dateUpdated": "2026-09-22T13:57:00.428Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-95666",
"date": "2026-09-24",
"epss": "0.00359",
"percentile": "0.26921"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Mattermost",
"vendor": "Mattermost",
"versions": [
{
"lessThanOrEqual": "11.9.1",
"status": "affected",
"version": "11.9.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.8.5",
"status": "affected",
"version": "11.8.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.7.10",
"status": "affected",
"version": "11.7.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.10.1",
"status": "affected",
"version": "11.10.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "11.11.0"
},
{
"status": "unaffected",
"version": "11.9.2"
},
{
"status": "unaffected",
"version": "11.8.6"
},
{
"status": "unaffected",
"version": "11.7.11"
},
{
"status": "unaffected",
"version": "11.10.2"
}
]
}
],
"source": "responsibledisclosure@mattermost.com"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771"
}
],
"id": "CVE-2026-95666",
"lastModified": "2026-09-22T19:32:25.730",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 4.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 1.4,
"source": "responsibledisclosure@mattermost.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-95666",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-22T13:55:15.216071Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-09-22T14:17:21.437",
"references": [
{
"source": "responsibledisclosure@mattermost.com",
"url": "https://mattermost.com/security-updates"
}
],
"sourceIdentifier": "responsibledisclosure@mattermost.com",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-770"
}
],
"source": "responsibledisclosure@mattermost.com",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-95666",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-22T13:55:15.216071Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-22T13:55:09.639Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Mattermost",
"vendor": "Mattermost",
"versions": [
{
"lessThanOrEqual": "11.9.1",
"status": "affected",
"version": "11.9.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.8.5",
"status": "affected",
"version": "11.8.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.7.10",
"status": "affected",
"version": "11.7.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.10.1",
"status": "affected",
"version": "11.10.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "11.11.0"
},
{
"status": "unaffected",
"version": "11.9.2"
},
{
"status": "unaffected",
"version": "11.8.6"
},
{
"status": "unaffected",
"version": "11.7.11"
},
{
"status": "unaffected",
"version": "11.10.2"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "idr"
}
],
"descriptions": [
{
"lang": "en",
"value": "Mattermost versions 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5, 11.7.x \u003c= 11.7.10, 11.10.x \u003c= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771"
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 4.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770: Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-22T13:11:13.798Z",
"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
"shortName": "Mattermost"
},
"references": [
{
"name": "MMSA-2026-00771",
"tags": [
"vendor-advisory"
],
"url": "https://mattermost.com/security-updates"
}
],
"solutions": [
{
"lang": "en",
"value": "Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher."
}
],
"source": {
"advisory": "MMSA-2026-00771",
"defect": [
"https://mattermost.atlassian.net/browse/MM-70177"
],
"discovery": "EXTERNAL"
},
"title": "Unbounded post ID array in the bulk reactions endpoint allows denial of service",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
"assignerShortName": "Mattermost",
"cveId": "CVE-2026-95666",
"datePublished": "2026-09-22T13:11:13.798Z",
"dateReserved": "2026-09-22T13:09:02.237Z",
"dateUpdated": "2026-09-22T13:57:00.428Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…