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Fencer Intel
critical 9.8

CVE-2025-50578 json

LinuxServer.io heimdall 2.6.3-ls307 contains a vulnerability in how it handles user-supplied HTTP headers, specifically `X-Forwarded-Host`…

published last yr. modified 4mo ago also EUVD-2025-23174

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known, plus a Nuclei check

Summary

LinuxServer.io heimdall 2.6.3-ls307 contains a vulnerability in how it handles user-supplied HTTP headers, specifically `X-Forwarded-Host` and `Referer`. An unauthenticated remote attacker can manipulate these headers to perform Host Header Injection and Open Redirect attacks. This allows the loading of external resources from attacker-controlled domains and unintended redirection of users, potentially enabling phishing, UI redress, and session theft. The vulnerability exists due to insufficient validation and trust of untrusted input, affecting the integrity and trustworthiness of the application.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
last yr.

Exploit prediction

3.10% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • Nuclei template Heimdall - Host Header Injection & Open Redirect nuclei detection template
  • medium.com https://medium.com/@juanfelipeoz.rar/cve-2025-50578-exploiting-host-header-injection-open-redirect-in-heimdall-application-733afceff2ea referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/linuxserver/Heimdall/issues/1451 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Classification

Weakness
  • CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component
  • CWE-601 URL Redirection to Untrusted Site
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.