medium CVSS 6.1 EPSS 0.27%

CVE-2026-48761·PHP vulnerability

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 6.1.0 until 6.4.41, 7.4.13, and 8.0.13, UrlAttributeSanitizer::getSupportedAttributes() omitted URL-bearing attributes on <object>, <applet>, <iframe>, and <img>, and <meta http-equiv="refresh"> URLs inside content bypassed URL sanitization, allowing explicitly enabled elements or attributes to pass javascript: and similar payloads into sanitized output. This issue is fixed in versions 6.4.41, 7.4.13, and 8.0.13.

Severity
medium
Software
PHP
Fixed in
8.0.13
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.27% — higher than 19% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

From: 8.0.0

Until: 8.0.13

Fixed in: 8.0.13

How to fix this CVE

Upgrade PHP to version 8.0.13 or later to patch the URL sanitization bypass in Symfony's UrlAttributeSanitizer component. This vulnerability allows malicious JavaScript payloads to bypass sanitization filters on HTML elements like <object>, <applet>, <iframe>, and <img>, as well as <meta http-equiv="refresh"> tags. Ensure your application dependencies are updated immediately after patching PHP.

sudo dnf update php php-common php-cli php-fpm

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET request parameters or form data containing HTML tags (<object|<applet|<iframe|<img) followed by event handlers or src attributes with javascript: protocol, or <meta http-equiv="refresh" content=".*javascript:.*">

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement WAF rules to block HTML input containing <object>, <applet>, <iframe>, or <img> tags with javascript: protocol handlers in src/href/data attributes, and block <meta> tags with http-equiv="refresh" containing javascript: payloads. Use Content Security Policy (CSP) headers with script-src 'self' to prevent inline script execution.

How to check if you are affected

  1. Step 1: Run `php -v` to check the current PHP version and confirm if it is between 8.0.0 and 8.0.12 (vulnerable range)
  2. Step 2: Check if Symfony framework is installed by running `composer show | grep symfony/symfony` or examining composer.lock for Symfony versions between 8.0.0-8.0.12
  3. Step 3: Search application logs for patterns like `<object`, `<applet`, `<iframe`, `<img`, or `http-equiv="refresh"` followed by `javascript:` payloads in user input or request parameters
  4. Step 4: After patching, verify PHP version is 8.0.13+ with `php -v` and confirm Symfony is updated to 8.0.13+ in composer.lock

FAQ

What is CVE-2026-48761?

CVE-2026-48761 is a URL sanitization bypass vulnerability in Symfony's UrlAttributeSanitizer that fails to properly filter dangerous URLs in certain HTML elements and attributes, allowing malicious JavaScript code to reach sanitized output when specific elements are explicitly enabled.

Is CVE-2026-48761 being actively exploited?

No, CVE-2026-48761 is not currently listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available, though the vulnerability poses a real risk if Symfony's URL sanitization is relied upon for security.

What versions of PHP are affected by CVE-2026-48761?

PHP versions 8.0.0 through 8.0.12 are affected when running Symfony framework versions 8.0.0 to 8.0.12. The vulnerability is fixed in PHP 8.0.13 and corresponding Symfony 8.0.13 release.

How do I check if my server is vulnerable to CVE-2026-48761?

Run `php -v` to check your PHP version, and run `composer show symfony/symfony` to verify the Symfony version. If PHP is 8.0.0-8.0.12 or Symfony is 8.0.0-8.0.12, your system is vulnerable.

Does Defensia detect CVE-2026-48761?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If PHP is installed on a monitored server, CVE-2026-48761 will appear in your dashboard with remediation steps.

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References

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