vulntracker.iovulntracker.io
© 2026 vulntracker.io

CVE-2025-20621

Webapp crash via object that can't be cast to String in Attachment Field

HIGH
7.5
CVSS Score
Published: January 16, 2025 at 06:16 PM UTC
Updated: June 17, 2026 at 08:41 AM UTC
2 products affected across 1 vendorMattermost ServerMattermost

Using Mattermost by Mattermost?

Get instant alerts when new vulnerabilities affect Mattermost - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Start FreeSign In
Severity
HIGH7.5
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly handle posts with attachments containing fields that cannot be cast to a String, which allows an attacker to cause the webapp to crash via creating and sending such a post to a channel.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mattermost Server· Mattermost
95%
10.0.0 ≤ v < 10.0.410.1.0 ≤ v < 10.1.49.11.0 ≤ v < 9.11.610.2.0
Mattermost· Mattermost
60%
10.0.0 ≤ v ≤ 10.0.310.1.0 ≤ v ≤ 10.1.39.11.0 ≤ v ≤ 9.11.510.0.010.1.010.2.09.11.0
Vendor states this is fixed in 10.0.4 (unaffected)
Vendor states this is fixed in 10.1.4 (unaffected)
Vendor states this is fixed in 10.2.1 (unaffected)
Vendor states this is fixed in 10.3.0 (unaffected)
Vendor states this is fixed in 2.23.0 (unaffected)
Vendor states this is fixed in 9.11.6 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisory
Source: [email protected]
https://mattermost.com/security-updates

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-1287

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create accountSign in
Free plan, no card