How severe is CVE-2025-55166?

No CVSS score has been assigned to CVE-2025-55166 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-55166?

CVE-2025-55166 affects the following packages: enshrined/svg-sanitize (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2025-55166?

Update enshrined/svg-sanitize to 0.22.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-55166 is resolved across your whole dependency graph.

How do I detect CVE-2025-55166 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for enshrined/svg-sanitize, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-55166 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2025-55166 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-55166 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-55166?

CVE-2025-55166 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 46th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-55166?

CVE-2025-55166 is classified as Cross-site Scripting (XSS) (CWE-79), Open Redirect (CWE-601). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2025-55166 published, and has it been updated?

CVE-2025-55166 was published on August 12, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2025-55166 — svg-sanitize

Fix: darylldoyle/svg-sanitizer@5a0a1ea

CVE-2025-55166 is a Cross-site Scripting (XSS) vulnerability in enshrined/svg-sanitize. A fix is available for enshrined/svg-sanitize — see the affected versions and patch details below.

svg-sanitizer By-Passing Attribute Sanitization

Also known asGHSA-22wq-q86m-83fh

Published

Aug 12, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-55166.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk+0.03%

Lower risk than most CVEs46th percentile — riskier than 46% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐘enshrined/svg-sanitize

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Problem

The sanitization logic at https://github.com/darylldoyle/svg-sanitizer/blob/0.21.0/src/Sanitizer.php#L454-L481 only searches for lower-case attribute names (e.g. xlink:href instead of xlink:HrEf), which allows to by-pass the isHrefSafeValue check. As a result this allows cross-site scripting or linking to external domains.

Proof-of-concept

provided by azizk

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="100" height="100">
  <a xlink:hReF="javascript:alert(document.domain)">
    <rect width="100" height="50" fill="red"></rect>
    <text x="50" y="30" text-anchor="middle" fill="white">Click me</text>
  </a>
</svg>

Credits

The mentioned findings and proof-of-concept example were reported to the TYPO3 Security Team by the external security researcher azizk <[email protected]>.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`enshrined/svg-sanitize`	all versions	0.22.0`composer require enshrined/svg-sanitize:^0.22.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for enshrined/svg-sanitize, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update enshrined/svg-sanitize to 0.22.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-55166 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

#### Problem The sanitization logic at https://github.com/darylldoyle/svg-sanitizer/blob/0.21.0/src/Sanitizer.php#L454-L481 only searches for lower-case attribute names (e.g. `xlink:href` instead of `xlink:HrEf`), which allows to by-pass the `isHrefSafeValue` check. As a result this allows cross-site scripting or linking to external domains. #### Proof-of-concept _provided by azizk_ ``` <?xml version="1.0" encoding="UTF-8"?> <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="100" height="100"> <a xlink:hReF="javascript:alert(document.domain)"> <r

O3 Security · Impact-Aware SCA

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