CVE-2026-40872
CVE-2026-40872 is a critical-severity vulnerability with a CVSS 4.0 base score of 9.3. 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: Critical (CVSS 4.0 base score 9.3)
- EPSS exploit prediction: 0% (20th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-24254
- 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 admin dashboard's Autodiscover logs render the EMailAddress value (logged as the "user" field) without HTML escaping. By submitting an unauthenticated Autodiscover request with a crafted EMailAddress containing HTML/JS, the payload is stored in Redis and executed when an admin views the Autodiscover logs. Version 2026-03b fixes the vulnerability.
Frequently asked questions
- What is CVE-2026-40872?
- mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the admin dashboard's Autodiscover logs render the EMailAddress value (logged as the "user" field) without HTML escaping. By submitting an unauthenticated Autodiscover request with a crafted EMailAddress containing HTML/JS, the payload is stored in Redis and executed when an admin views the Autodiscover logs. Version 2026-03b fixes the vulnerability.
- How severe is CVE-2026-40872?
- CVE-2026-40872 has a CVSS 4.0 base score of 9.3, rated critical severity.
- Is CVE-2026-40872 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-40872?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
- Does CVE-2026-40872 have an EU (EUVD) identifier?
- Yes. CVE-2026-40872 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24254.
- When was CVE-2026-40872 published?
- CVE-2026-40872 was published on 2026-04-21 and last updated on 2026-06-17.
References
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