CVE-2026-40878
CVE-2026-40878 is a low-severity vulnerability with a CVSS 4.0 base score of 2.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.
Key facts
- Severity: Low (CVSS 4.0 base score 2.1)
- EPSS exploit prediction: 1% (52nd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-24262
- Weakness: CWE-79
- Published:
- Last modified:
Description
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.
Frequently asked questions
- What is CVE-2026-40878?
- 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.
- How severe is CVE-2026-40878?
- CVE-2026-40878 has a CVSS 4.0 base score of 2.1, rated low severity.
- Is CVE-2026-40878 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-40878?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-40878 have an EU (EUVD) identifier?
- Yes. CVE-2026-40878 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24262.
- When was CVE-2026-40878 published?
- CVE-2026-40878 was published on 2026-04-21 and last updated on 2026-06-17.
References
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