CVE-2026-25783— Denial of service via malformed User-Agent header in getBrowserVersion
Quick assessment
Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost 11.3.0及之前的11.3.x版本、11.2.2及之前的11.2.x版本和10.11.10及之前的10.11.x版本存在安全漏洞，该漏洞源于未正确验证User-Agent标头令牌，可能导致经过身份验证的攻击者通过特制User-Agent标头引发请求恐慌。
Possible ATT&CK Techniques 1 AI
T1190 · Exploit Public-Facing Application
Get alerts for future matching vulnerabilities
Log in to subscribe
I. Basic Information for CVE-2026-25783
Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗
Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.
Vulnerability Title
Denial of service via malformed User-Agent header in getBrowserVersion
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a request panic via a specially crafted User-Agent header. Mattermost Advisory ID: MMSA-2026-00586
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1287
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost 11.3.0及之前的11.3.x版本、11.2.2及之前的11.2.x版本和10.11.10及之前的10.11.x版本存在安全漏洞，该漏洞源于未正确验证User-Agent标头令牌，可能导致经过身份验证的攻击者通过特制User-Agent标头引发请求恐慌。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 11.3.0 ~ 11.3.0 | - |
|
II. Public POCs for CVE-2026-25783
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
Premium
No public POC found.
Login to generate AI POCIII. Intelligence Information for CVE-2026-25783
请登录查看更多情报信息。
Same Patch Batch · Mattermost · 2026-03-16 · 21 CVEs total
| CVE-2026-2476 | 7.6 HIGH | MS Teams plugin sensitive config values not properly masked in support packets |
| CVE-2026-24458 | 7.5 HIGH | DoS attack via login attempts with multi-megabyte passwords |
| CVE-2026-2462 | 6.6 MEDIUM | Admin RCE via Malicious Plugin Upload on CI Test Instances |
| CVE-2026-2454 | 5.8 MEDIUM | DoS in Calls plugin via malformed msgpack in websocket request. |
| CVE-2026-2456 | 5.3 MEDIUM | Denial of Service via Unbounded Memory Allocation in Integration Actions |
| CVE-2026-2455 | 4.3 MEDIUM | SSRF bypass via IPv4-mapped IPv6 literals |
| CVE-2026-21386 | 4.3 MEDIUM | Private channel enumeration via /mute slash command |
| CVE-2026-25780 | 4.3 MEDIUM | Memory Exhaustion via Malformed DOC File Upload |
| CVE-2026-4265 | 4.3 MEDIUM | Guest user can upload files without permission across teams |
| CVE-2026-24692 | 4.3 MEDIUM | Guest users can bypass read permissions via search API |
| CVE-2026-26304 | 4.3 MEDIUM | Permission Bypass in Playbook Run Creation |
| CVE-2026-2578 | 4.3 MEDIUM | Information Disclosure via WebSocket Event When Deleting Unrevealed Burn on Read Posts |
| CVE-2026-26246 | 4.3 MEDIUM | Memory Exhaustion via Malformed PSD File Upload |
| CVE-2026-2458 | 4.3 MEDIUM | Unauthorized channel enumeration in private teams after member removal |
| CVE-2026-2457 | 4.3 MEDIUM | WebSocket Message Spoofing via Permalink Embed Manipulation |
| CVE-2026-2461 | 4.3 MEDIUM | Missing authorization check allows unauthorized modification of other users' comments on a |
| CVE-2026-2463 | 4.3 MEDIUM | Unauthorized access to invite ID during team creation |
| CVE-2026-1629 | 4.3 MEDIUM | Permalink Preview Information Disclosure After Permission Revocation |
| CVE-2026-26230 | 3.8 LOW | Team Admin Privilege Escalation to Demote Members to Guest |
| CVE-2026-22545 | 3.1 LOW | Password Change Bypass via Auth Switch Endpoint |
IV. Related Vulnerabilities
Same product: Mattermost
-
CVE-2026-96260
Mattermost server missing request body size limit on plugin -
CVE-2026-96259
Mattermost server-side request forgery via OAuth endpoints c -
CVE-2026-95666
Unbounded post ID array in the bulk reactions endpoint allow -
CVE-2026-12284
Mattermost Desktop App Missing IPC Sender Validation in Call -
CVE-2026-75588
Mattermost Desktop App plugin popout scheme validation bypas
Same vendor: Mattermost
-
CVE-2026-96260
Mattermost server missing request body size limit on plugin -
CVE-2026-96259
Mattermost server-side request forgery via OAuth endpoints c -
CVE-2026-95666
Unbounded post ID array in the bulk reactions endpoint allow -
CVE-2026-12284
Mattermost Desktop App Missing IPC Sender Validation in Call -
CVE-2026-75588
Mattermost Desktop App plugin popout scheme validation bypas
Same weakness: CWE-1287
-
CVE-2026-75588
Mattermost Desktop App plugin popout scheme validation bypas -
CVE-2026-89207
WTV系列设备未验证输入致拒绝服务漏洞 -
CVE-2026-86287
Net::IP::LPM versions before 1.12 for Perl accept malformed -
CVE-2026-82741
Ash.Type.Union with :map_with_tag does not force the tag on -
CVE-2026-80051
graphql-go project graphql-go 软件供应链问题漏洞
V. Comments for CVE-2026-25783
No comments yet