Is there a public PoC exploit available for CVE-2026-40878?

Yes, a public proof-of-concept exploit is available for CVE-2026-40878. Prioritise patching immediately. EPSS: 0.0%.

Is there a patch available for CVE-2026-40878?

Yes, a patch is available for CVE-2026-40878. Update the affected software to the latest version immediately.

Docker CVE-2026-40878

Q: What is the CVSS score of CVE-2026-40878?

CVE-2026-40878 has a CVSS 4.0 base score of 2.1 (Low). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.0%.

EUVD-2026-24262 LOW

Cross-site Scripting (XSS) (CWE-79)

2026-04-21 GitHub_M

XSS Docker

2.1

CVSS 4.0 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

2.1 LOW

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Scope

Lifecycle Timeline

Patch released

Apr 22, 2026 - 21:02 nvd

Patch available

Apr 21, 2026 - 21:02 EUVD

CVSS changed

Apr 21, 2026 - 20:22 NVD

2.1 (LOW)

EUVD ID Assigned

Apr 21, 2026 - 20:00 euvd

EUVD-2026-24262

CVE Published

Apr 21, 2026 - 19:21 nvd

LOW 2.1

DescriptionGitHub Advisory

mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the mailcow web interface passes the raw $_SERVER['REQUEST_URI'] to Twig as a global template variable and renders it inside a JavaScript string literal in the setLang() helper of base.twig, relying on Twig's default HTML auto-escaping instead of the context-appropriate js escaping strategy. In addition, the query_string() Twig helper merges all current $_GET parameters into the language-switching links on the login page, so attacker-supplied parameters are reflected and preserved across navigation. Version 2026-03b fixes the vulnerability.

Analysis

mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the mailcow web interface passes the raw $_SERVER['REQUEST_URI'] to Twig as a global template variable and renders it inside a JavaScript string literal in the setLang() helper of base.twig, relying on Twig's default HTML auto-escaping instead of the context-appropriate js escaping strategy. …

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CVE-2026-40878 vulnerability details – vuln.today

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