CVE-2023-51803Network attack vector

PHP content upload via unvalidated icons

Published Mar 31, 2024 · Updated Aug 20, 2024

Improper file validation in LinuxServer.io Heimdall before 2.5.7 allows remote attackers to upload non-image icon content. The item-icon upload path accepts content containing PHP syntax without establishing that the submitted data is an image. An exposed item-management interface provides the network gate; accepted content is stored as an icon, but public sources do not establish server-side execution.

CVSS severity9.8
Critical
EPSS probability0.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper file validation in LinuxServer.io Heimdall before 2.5.7 allows remote attackers to upload non-image icon content. The item-icon upload path accepts content containing PHP syntax without establishing that the submitted data is an image. An exposed item-management interface provides the network gate; accepted content is stored as an icon, but public sources do not establish server-side execution.

The record

CVE
CVE-2023-51803
Published
Mar 31, 2024
Updated
Aug 20, 2024
Vendor
LinuxServer.io
Product
Heimdall
Classifications
CWE-674
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 31, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <2.5.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LinuxServer.io · Heimdallversion=0 <2.5.7

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-674Uncontrolled Recursion

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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