CVE-2026-2455
SSRF Vulnerability in Mattermost via IPv4-Mapped IPv6 Address Handling
Publication date: 2026-03-16
Last updated on: 2026-03-18
Assigner: Mattermost, Inc.
Description
Description
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mattermost | mattermost_server | From 10.11.0 (inc) to 10.11.11 (exc) |
| mattermost | mattermost_server | From 11.2.0 (inc) to 11.2.3 (exc) |
| mattermost | mattermost_server | From 11.3.0 (inc) to 11.3.1 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-918 | The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in certain versions of Mattermost (11.3.x <= 11.3.0, 11.2.x <= 11.2.2, and 10.11.x <= 10.11.10) where the software fails to properly canonicalize IPv4-mapped IPv6 addresses before performing reserved IP validation.
Because of this failure, an attacker can exploit the system by using IPv4-mapped IPv6 literals (for example, [::ffff:127.0.0.1]) to bypass IP address checks and perform Server-Side Request Forgery (SSRF) attacks against internal services.
How can this vulnerability impact me? :
This vulnerability can allow an attacker with limited privileges to perform SSRF attacks, potentially accessing internal services that are not intended to be exposed externally.
Such SSRF attacks could lead to unauthorized access to internal resources, information disclosure, or further exploitation within the internal network.
The CVSS score of 4.3 indicates a low to medium severity impact, with limited confidentiality impact and no impact on integrity or availability.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
I don't know