CVE-2025-50578: LinuxServer.io heimdall 2.6.3-ls307 contains a vulnerability in how it handles user-supplied HTTP headers, spe

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CRITICAL 9.8REMOTEWATCHLISTDOWNGRADE

CVE-2025-50578 is a critical-severity flaw (CVSS 9.8) affecting docker-heimdall. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 t

Why this priority

Critical severity
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.0% (top 13%)
CISA exploited list	No
Weakness	CWE-20, CWE-74, CWE-601
Published	2025-07-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: linuxserver

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-07-30 16:15 UTCPublished CVE record published
2026-06-17 09:35 UTCUpdated Record last modified

linuxserver docker-heimdall DOWNGRADE

Affected: 2.6.3-ls307

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.6.3-ls307

1. Check installed version

apt-cache policy docker-heimdall || rpm -q docker-heimdall || docker-heimdall --version

2. No fixed release: DOWNGRADE to a release before 2.6.3-ls307 (Debian / Ubuntu)

apt-cache madison docker-heimdall sudo apt install docker-heimdall=<VERSION_BEFORE_2.6.3-ls307> sudo apt-mark hold docker-heimdall

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list docker-heimdall sudo dnf downgrade docker-heimdall-<VERSION_BEFORE_2.6.3-ls307> sudo dnf versionlock add docker-heimdall

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · R · FIXED · 4.6.2-1.fc46 · FEDORA-2026-1dd919a262 · source

sudo dnf upgrade --advisory=FEDORA-2026-1dd919a262

Fedora ELN · perl-Mail-AuthenticationResults · FIXED · 2.20261029-1.eln159 · FEDORA-2026-a2c11d7da6 · source

sudo dnf upgrade --advisory=FEDORA-2026-a2c11d7da6

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/linuxserver/Heimdall/issues/1451
Write-up: medium.com/@juanfelipeoz.rar/cve-2025-50578-exploiting-host-header-injection-open-redirect
Nuclei scan template: Heimdall - Host Header Injection & Open Redirect

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-50578?

docker-heimdall: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-50578 being exploited?

CVE-2025-50578 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-50578 affect?

CVE-2025-50578 affects docker-heimdall. Severity is critical (CVSS 9.8). 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

How urgent is CVE-2025-50578?

Priority 74/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Docker vulnerabilities

References

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