CVE-2026-4635 (GCVE-0-2026-4635)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:28 – Updated: 2026-05-22 12:06
VLAI
EPSS
VEX
Title
Persistent notification timing attack causing server denial of service
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637
Severity
6.5 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-22 12:06 UTC
CWE
- CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-4635",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-22T12:06:11.038792Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-22T12:06:16.773Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Mattermost",
"vendor": "Mattermost",
"versions": [
{
"lessThanOrEqual": "11.6.0",
"status": "affected",
"version": "11.6.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.5.3",
"status": "affected",
"version": "11.5.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "11.4.4",
"status": "affected",
"version": "11.4.0",
"versionType": "semver"
},
{
"lessThanOrEqual": "10.11.14",
"status": "affected",
"version": "10.11.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "11.7.0"
},
{
"status": "unaffected",
"version": "11.6.1"
},
{
"status": "unaffected",
"version": "11.5.4"
},
{
"status": "unaffected",
"version": "11.4.5"
},
{
"status": "unaffected",
"version": "10.11.15"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "daw10"
}
],
"descriptions": [
{
"lang": "en",
"value": "Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637"
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 6.5,
"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:H",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-362",
"description": "CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-22T10:28:47.634Z",
"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
"shortName": "Mattermost"
},
"references": [
{
"name": "MMSA-2026-00637",
"tags": [
"vendor-advisory"
],
"url": "https://mattermost.com/security-updates"
}
],
"solutions": [
{
"lang": "en",
"value": "Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher."
}
],
"source": {
"advisory": "MMSA-2026-00637",
"defect": [
"https://mattermost.atlassian.net/browse/MM-68023"
],
"discovery": "EXTERNAL"
},
"title": "Persistent notification timing attack causing server denial of service",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
"assignerShortName": "Mattermost",
"cveId": "CVE-2026-4635",
"datePublished": "2026-05-22T10:28:47.634Z",
"dateReserved": "2026-03-23T08:41:57.555Z",
"dateUpdated": "2026-05-22T12:06:16.773Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-4635",
"date": "2026-08-12",
"epss": "0.00172",
"percentile": "0.06875"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-4635\",\"sourceIdentifier\":\"responsibledisclosure@mattermost.com\",\"published\":\"2026-05-22T11:16:22.747\",\"lastModified\":\"2026-07-23T16:10:00.137\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637\"},{\"lang\":\"es\",\"value\":\"Las versiones de Mattermost 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 no archivan el canal antes de eliminar las notificaciones persistentes, lo que permite a un usuario autenticado colapsar el servidor al cronometrar la creaci\u00f3n de un mensaje de notificaci\u00f3n persistente entre el momento en que el servidor elimina las notificaciones persistentes existentes y archiva el canal. ID de aviso de Mattermost: MMSA-2026-00637\"}],\"affected\":[{\"source\":\"responsibledisclosure@mattermost.com\",\"affectedData\":[{\"vendor\":\"Mattermost\",\"product\":\"Mattermost\",\"defaultStatus\":\"unaffected\",\"versions\":[{\"version\":\"11.6.0\",\"lessThanOrEqual\":\"11.6.0\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"11.5.0\",\"lessThanOrEqual\":\"11.5.3\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"11.4.0\",\"lessThanOrEqual\":\"11.4.4\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"10.11.0\",\"lessThanOrEqual\":\"10.11.14\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"11.7.0\",\"status\":\"unaffected\"},{\"version\":\"11.6.1\",\"status\":\"unaffected\"},{\"version\":\"11.5.4\",\"status\":\"unaffected\"},{\"version\":\"11.4.5\",\"status\":\"unaffected\"},{\"version\":\"10.11.15\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"responsibledisclosure@mattermost.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":6.5,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.8,\"impactScore\":3.6},{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.6,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-05-22T12:06:11.038792Z\",\"id\":\"CVE-2026-4635\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"responsibledisclosure@mattermost.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-362\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"10.11.0\",\"versionEndExcluding\":\"10.11.15\",\"matchCriteriaId\":\"6696A83A-CD06-45BD-A4C1-16A09C4CA15B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"11.4.0\",\"versionEndExcluding\":\"11.4.5\",\"matchCriteriaId\":\"AB489375-1F54-4A24-AE2C-37D92B27FF4D\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"11.5.0\",\"versionEndExcluding\":\"11.5.4\",\"matchCriteriaId\":\"617D4791-A087-42E8-BF73-B39B30CB29C8\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"11.6.0\",\"versionEndExcluding\":\"11.6.1\",\"matchCriteriaId\":\"77708744-DCB4-4AE3-8146-CB043DAB6FBB\"}]}]}],\"references\":[{\"url\":\"https://mattermost.com/security-updates\",\"source\":\"responsibledisclosure@mattermost.com\",\"tags\":[\"Vendor Advisory\"]}]}}",
"redhat_vex": {
"current_release_date": "2026-06-05T19:28:18+00:00",
"cve": "CVE-2026-4635",
"id": "CVE-2026-4635",
"initial_release_date": "2026-01-01T00:00:00+00:00",
"product_status:known_not_affected": "1",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "Persistent notification timing attack causing server denial of service",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4635.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-07-31T00:54:53Z",
"cve": "CVE-2026-4635",
"id": "CVE-2026-4635",
"initial_release_date": "2026-07-31T00:54:53Z",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-4635",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-4635.json",
"version": "2"
},
"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-4635\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-22T12:06:11.038792Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-22T12:06:13.664Z\"}}], \"cna\": {\"title\": \"Persistent notification timing attack causing server denial of service\", \"source\": {\"defect\": [\"https://mattermost.atlassian.net/browse/MM-68023\"], \"advisory\": \"MMSA-2026-00637\", \"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"daw10\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 6.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"Mattermost\", \"product\": \"Mattermost\", \"versions\": [{\"status\": \"affected\", \"version\": \"11.6.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"11.6.0\"}, {\"status\": \"affected\", \"version\": \"11.5.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"11.5.3\"}, {\"status\": \"affected\", \"version\": \"11.4.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"11.4.4\"}, {\"status\": \"affected\", \"version\": \"10.11.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"10.11.14\"}, {\"status\": \"unaffected\", \"version\": \"11.7.0\"}, {\"status\": \"unaffected\", \"version\": \"11.6.1\"}, {\"status\": \"unaffected\", \"version\": \"11.5.4\"}, {\"status\": \"unaffected\", \"version\": \"11.4.5\"}, {\"status\": \"unaffected\", \"version\": \"10.11.15\"}], \"defaultStatus\": \"unaffected\"}], \"solutions\": [{\"lang\": \"en\", \"value\": \"Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.\"}], \"references\": [{\"url\": \"https://mattermost.com/security-updates\", \"name\": \"MMSA-2026-00637\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-362\", \"description\": \"CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee\", \"shortName\": \"Mattermost\", \"dateUpdated\": \"2026-05-22T10:28:47.634Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-4635\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-22T12:06:16.773Z\", \"dateReserved\": \"2026-03-23T08:41:57.555Z\", \"assignerOrgId\": \"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee\", \"datePublished\": \"2026-05-22T10:28:47.634Z\", \"assignerShortName\": \"Mattermost\"}",
"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…
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.
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.
Loading…
Loading…