Summary
Symfony Vulnerable to stored XSS in WebProfiler CodeExtension::fileExcerpt(), Unescaped Non-PHP File Rendering
Description
Symfony's profiler, a development only debug UI, renders source-code excerpts on several pages using Twig's custom file_excerpt filter. This filter renders PHP files via highlight_string() (which escapes HTML), but renders non-PHP files by splitting on \n and interpolating each line directly into <code>{$line}</code> with no escaping.
An attacker who can write arbitrary bytes into any file under the project root (including e.g. var/log/dev.log), achieves stored XSS against any developer who later opens that file in the profiler.
Resolution
The file_excerpt filter now properly escapes each line of non-PHP files using htmlspecialchars() before concatenating them.
The patch for this issue is available here for branch 6.4.
Credits
Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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symfony/symfony to 6.4.40 or later; symfony/symfony to 7.4.12 or later; symfony/symfony to 8.0.12 or later; symfony/twig-bridge to 6.4.40 or later; symfony/web-profiler-bundle to 7.4.12 or later; symfony/web-profiler-bundle to 8.0.12 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-45072? CVE-2026-45072 is a low-severity cross-site scripting (XSS) vulnerability in symfony/symfony (composer), affecting versions >= 6.4.24, < 6.4.40. It is fixed in 6.4.40, 7.4.12, 8.0.12. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which packages are affected by CVE-2026-45072?
symfony/symfony(composer) (versions >= 6.4.24, < 6.4.40)symfony/twig-bridge(composer) (versions >= 6.4.24, < 6.4.40)symfony/web-profiler-bundle(composer) (versions >= 7.2.9, < 7.4.12)
- Is there a fix for CVE-2026-45072? Yes. CVE-2026-45072 is fixed in 6.4.40, 7.4.12, 8.0.12. Upgrade to this version or later.
- Is CVE-2026-45072 exploitable, and should I be worried? Whether CVE-2026-45072 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-45072 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-45072?
- Upgrade
symfony/symfonyto 6.4.40 or later - Upgrade
symfony/symfonyto 7.4.12 or later - Upgrade
symfony/symfonyto 8.0.12 or later - Upgrade
symfony/twig-bridgeto 6.4.40 or later - Upgrade
symfony/web-profiler-bundleto 7.4.12 or later - Upgrade
symfony/web-profiler-bundleto 8.0.12 or later
- Upgrade