Get a Demo

Let's Patch It!

Book a short call with one our specialists, we'll walk you through how Endor Patches work, and ask you a few questions about your environment (like your primary programming languages and repository management). We'll also send you an email right after you fill out the form, feel free to reply with any questions you have in advance!

CVE

CVE-2026-85751

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

CVE-2026-85751

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

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 PROXYAUTHWHITELIST configured but REALIPHEADER unset trusted a client-controlled X-Forwarded-By header for header-based proxy authentication. The proxyhideheader 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.

Package Versions Affected

Package Version
patch Availability
No items found.

Automatically patch vulnerabilities without upgrading

Fix Without Upgrading
Detect compatible fix
Apply safe remediation
Fix with a single pull request

CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9.8
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
C
H
U
0
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
C
H
U
-

Related Resources

No items found.

References

https://github.com/Mailu/Mailu/releases/tag/2024.06.55, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85751.json, https://github.com/Mailu/Mailu/security/advisories/GHSA-rfhj-4wcq-74xg, https://nvd.nist.gov/vuln/detail/CVE-2026-85751, https://github.com/Mailu/Mailu/commit/dffa97cbd889ab208246372ce9c86e99abb27ae9, https://github.com/Mailu/Mailu/commit/ff4003d045753013470945336448dbd790cac778, https://github.com/Mailu/Mailu/pull/4070, https://github.com/Mailu/Mailu/pull/4071

Severity

9.8

CVSS Score
0
10

Basic Information

Base CVSS
9.8
EPSS Probability
0.00557%
EPSS Percentile
0.45355%
Introduced Version
d65b15abb73eeca0516de0ec3582441debab70de
Fix Available
d5f034588cce82abee6251ca4e0e0048b1c82a8c

Fix Critical Vulnerabilities Instantly

Secure your app without upgrading.
Fix Without Upgrading