VDB-351280 · CVE-2026-2455 · EUVD-2026-12441

Mattermost up to 10.11.10/11.2.2/11.3.0/11.3.x IPv6 Address server-side request forgery

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.2	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.10/11.2.2/11.3.0/11.3.x. It has been declared as critical. The affected element is an unknown function of the component IPv6 Address Handler. Executing a manipulation can lead to server-side request forgery. This vulnerability is registered as CVE-2026-2455. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Mattermost up to 10.11.10/11.2.2/11.3.0/11.3.x. This vulnerability affects some unknown processing of the component IPv6 Address Handler. The manipulation with an unknown input leads to a server-side request forgery vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation which allows an attacker to perform SSRF attacks against internal services via IPv4-mapped IPv6 literals (e.g., [::ffff:127.0.0.1]).. Mattermost Advisory ID: MMSA-2026-00585

The weakness was published by winfunc. The advisory is shared for download at mattermost.com. This vulnerability was named CVE-2026-2455 since 02/13/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are neither technical details nor an exploit publicly available.

Upgrading to version 10.11.11, 11.2.3, 11.3.1 or 11.4.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-12441). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

Groupware Software

Name

Mattermost

Version

License

open-source

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.2

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.3
CNA Vector (Mattermost): 🔒

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Server-side request forgery
CWE: CWE-918
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.11/11.2.3/11.3.1/11.4.0

Timelineinfo

02/13/2026 CVE reserved
03/16/2026 +31 days Advisory disclosed
03/16/2026 +0 days VulDB entry created
03/21/2026 +5 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: winfunc
Status: Confirmed

CVE: CVE-2026-2455 (🔒)
GCVE (CVE): GCVE-0-2026-2455
GCVE (VulDB): GCVE-100-351280
EUVD: 🔒

Entryinfo

Created: 03/16/2026 16:16
Updated: 03/21/2026 11:50
Changes: 03/16/2026 16:16 (65), 03/16/2026 18:32 (1), 03/21/2026 11:50 (1)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.