How severe is CVE-2015-5956?

No CVSS score has been assigned to CVE-2015-5956 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2015-5956?

CVE-2015-5956 affects the following packages: typo3/cms (Packagist), typo3/cms (Packagist), typo3/cms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2015-5956?

Update typo3/cms to 6.2.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-5956 is resolved across your whole dependency graph.

How do I detect CVE-2015-5956 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2015-5956 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-2015-5956 actively exploited in the wild?

No public exploit code has been indexed for CVE-2015-5956 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-2015-5956?

CVE-2015-5956 has an EPSS (Exploit Prediction Scoring System) score of 2.0%, placing it in the 81th 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-2015-5956?

CVE-2015-5956 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type 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-2015-5956 published, and has it been updated?

CVE-2015-5956 was published on May 14, 2022 and was last updated on December 7, 2024. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2015-5956: cms XSS — Fixed in 6.2.15

EPSS Exploitation Probability

via FIRST.org ↗

2.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs81th percentile — riskier than 81% of all scored CVEsHighest risk

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

Real-World Exposure

3 pkgs affected

🐘typo3/cms🐘typo3/cms🐘typo3/cms

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

The sanitizeLocalUrl function in TYPO3 6.x before 6.2.15, 7.x before 7.4.0, 4.5.40, and earlier allows remote authenticated users to bypass the XSS filter and conduct cross-site scripting (XSS) attacks via a base64 encoded data URI, as demonstrated by the (1) returnUrl parameter to show_rechis.php and the (2) redirect_url parameter to index.php.

Affected Packages

3 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`typo3/cms`	≥ 6.0&&< 6.2.15	6.2.15`composer require typo3/cms:^6.2.15`
🐘Packagist	`typo3/cms`	≥ 7.0&&< 7.4.0	7.4.0`composer require typo3/cms:^7.4.0`
🐘Packagist	`typo3/cms`	≥ 4.0	No fix

Affected Products

1 product · 48 configurations

Application

typo3typo3

≤ 4.5.40

45 versions

6.06.0.16.0.26.0.36.0.46.0.56.0.66.0.76.0.86.0.96.0.106.0.11

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update typo3/cms to 6.2.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-5956 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

The sanitizeLocalUrl function in TYPO3 6.x before 6.2.15, 7.x before 7.4.0, 4.5.40, and earlier allows remote authenticated users to bypass the XSS filter and conduct cross-site scripting (XSS) attacks via a base64 encoded data URI, as demonstrated by the (1) returnUrl parameter to show_rechis.php and the (2) redirect_url parameter to index.php.

O3 Security · Impact-Aware SCA

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CVE-2015-5956 — cms