# CVE-2026-125757: mailcow: dockerized before 2026-11 Template Injection RCE via Domain-Wide Footer

Status: published. Published: 2026-11-10. Updated: 2026-11-10.

mailcow: dockerized before 2026-11 contains a server-side template injection vulnerability that allows domain administrators to execute commands in the shared rspamd container by storing a malicious domain-wide footer. Attackers can embed a Jinja macro with an os.execute default value, rendered by the rspamd MOO_FOOTER prefilter, to read or inject mail for every tenant and disable filtering.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/mailcow/mailcow-dockerized/commit/e986803980db8b29435a2ddba5d9760737a818e3

## Affected products and versions

- mailcow / mailcow: dockerized (mailcow/mailcow-dockerized): ≥ 0; < 2026-11 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 9.4 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H; source: CNA: VulnCheck

- CVSS 3.1: 9.1 (critical); CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H; source: CNA: VulnCheck

- CVSS 4.0: 9.4 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 9.1 (critical); CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation poc; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-1336

## Exploit evidence

- exploit: https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jgr3-fv33-x43c (ADP: CISA-ADP)

## References

- https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jgr3-fv33-x43c (CNA: VulnCheck; vendor-advisory)

- https://github.com/mailcow/mailcow-dockerized/commit/e986803980db8b29435a2ddba5d9760737a818e3 (CNA: VulnCheck; patch)

- https://github.com/mailcow/mailcow-dockerized/releases/tag/2026-11 (CNA: VulnCheck; release-notes)

- https://github.com/mailcow/mailcow-dockerized/blob/55982ac74bfd35581cc44b122ab5fc659e3ae90a/data/conf/rspamd/lua/rspamd.local.lua#L847-L850 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/mailcow-dockerized-before-2026-11-template-injection-rce-via-domain-wide-footer (CNA: VulnCheck; third-party-advisory)

- https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jgr3-fv33-x43c (ADP: CISA-ADP; exploit)

- https://github.com/mailcow/mailcow-dockerized/blob/55982ac74bfd35581cc44b122ab5fc659e3ae90a/data/conf/rspamd/lua/rspamd.local.lua#L847-L850 (disclosure@vulncheck.com)

- https://github.com/mailcow/mailcow-dockerized/commit/e986803980db8b29435a2ddba5d9760737a818e3 (disclosure@vulncheck.com)

- https://github.com/mailcow/mailcow-dockerized/releases/tag/2026-11 (disclosure@vulncheck.com)

- https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jgr3-fv33-x43c (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/mailcow-dockerized-before-2026-11-template-injection-rce-via-domain-wide-footer (disclosure@vulncheck.com)

- https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jgr3-fv33-x43c (134c704f-9b21-4f2e-91b3-4a467353bcc0)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-125757; retrieved 2026-11-10; source updated 2026-11-10

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-125757; retrieved 2026-11-10; source updated 2026-11-10

Revision: 3b84de0404935d0434e8ac0efa066b86da092141330f1b3a00f1a6beedff3f35

Canonical: https://y2.dev/cve/CVE-2026-125757

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.