What is CVE-2026-9693?

CVE-2026-9693 is Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite. The supplied enrichment data classifies it as Remote Code Exec mapped to CWE-459 CWE-459.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-9693. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-9693 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

3 public PoC repositories reported; 0 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS, EDR process telemetry, host service logs where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-9693 using CVSS 3.5, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

Workarounds are not confirmed from current sources. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

lowRemote Code Execpublic exploit

CVE-2026-9693

CVE-2026-9693 — Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682

Published Aug 17, 2026Updated Aug 17, 2026Sources: NVD, Mattermost (CNA), GitHub, GitHub Security Advisory, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

ahead of 0% of scored CVEs

Affects

Mattermost

5 products listed

CVSS base

3.5

low

Remediation

The vendor's own words where we have them.

Update Mattermost to versions 11.9.0, 10.11.21, 11.7.6 or higher.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Mattermost	Mattermost	10.11.0 to <= 10.11.20	Vulnerable
Mattermost	Mattermost	11.7.0 to <= 11.7.5	Vulnerable
Mattermost	Mattermost	11.9.0	Patched
Mattermost	Mattermost	10.11.21	Patched
Mattermost	Mattermost	11.7.6	Patched

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

None

Confidentiality

Low

Integrity

None

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Network

Privileges Req

Low

User Interaction

Required

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
3.5	CVSS 3.1	low	2.1	1.4	mattermost.com (CNA), Mattermost (CNA), GHSA

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-459 · Incomplete Cleanup

Other
Read Application Data
Modify Application Data
DoS: Resource Consumption (Other)

Mitigation: Temporary files and other supporting resources should be deleted/released immediately after they are no longer needed.::

Weakness & attack patterns

CWE-459

Inferred from the weakness class — not observed against this CVE.

CAPEC-242 · Code InjectionCAPEC-35 · Leverage Executable Code in Non-Executable Files

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

Social mentions

Posts naming this CVE. Attention, not evidence of exploitation — it spikes on disclosure and decays whether or not anything is exploited.

CVE-2026-9693 Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allow… https://t.co/E7xEMi8tzp
@CVEnew· Aug 17, 2026

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable Mattermost.
Monitor for scanner or exploit-pattern traffic after 3 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPSEDR process telemetryhost service logs

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · GHSA-f5mp-j4vf-9jp4 published (low)
Aug 18, 2026 · GitHub Security Advisory
Added · CVSS 3.1 3.5 (AV:N)
Aug 17, 2026 · NVD
Initial · CVE published
Aug 17, 2026 · NVD

Source activity

Readings a source repeats on a schedule, counted rather than listed.

1×CVE modified by NIST, Modified, LinkAug 18, 2026 · SOCRadar CTI

References

3 on the record

mattermost.com/security-updates
Vendor Advisory, Mitre, NIST
nvd.nist.gov/vuln/detail/CVE-2026-9693
NVD
github.com/advisories/GHSA-f5mp-j4vf-9jp4
Exploit, Third Party Advisory

Elsewhere on this site

Mattermostevery CVE for this vendor
Remote Code Execsame class
CWE-459other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-9693 is Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite, a low vulnerability affecting Mattermost from Mattermost. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-9693. Public exploit evidence is: 3 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 3.5 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.