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CVE-2026-85751

Mailu: Authentication bypass in header-based proxy authentication via spoofable `X-Forwarded-By` trust

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 2024.06.55, 2.7.3
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

Mailu is a mail server distributed as a set of Docker images. From Mailu 2.0 until 2024.06.55 and prior to Mailu helm-charts 2.7.3, deployments with PROXY_AUTH_WHITELIST configured but REAL_IP_HEADER unset trusted a client-controlled X-Forwarded-By header for header-based proxy authentication. The proxy_hide_header directive in the nginx template at core/nginx/conf/proxy.conf hid the header from upstream responses but did not overwrite the incoming request value in this configuration. An unauthenticated remote attacker could therefore spoof the trusted proxy identity and bypass authentication. This issue is fixed in Mailu 2024.06.55 and Mailu helm-charts 2.7.3.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Mailu Mailu

    From 2.0.0 · fixed in 2024.06.55

  • Mailu helm-charts

    fixed in 2.7.3

References 6

GitHub · Mailu/Mailu