Summary
symfony/ux-toolkit: Path Traversal Allows Arbitrary File Write and Read via Crafted Recipe Manifest
Description
The ux:install console command installs files from a recipe kit by copying paths listed in a copy-files map. The only guard against malicious paths was Path::isRelative(), which returns true for paths like ../../../etc. Path::join() then resolves the .. segments without complaint, so the final path can escape the intended directory entirely. A crafted or compromised kit can therefore write attacker-controlled content to arbitrary locations on the developer's machine or CI runner.
Because the copy operation creates missing parent directories and can overwrite existing files silently (with --force or in non-interactive environments), an attacker who controls a kit can overwrite files such as controllers, git hooks, or .env to achieve code execution. The source side of copy-files is symmetrically affected, enabling local file reads outside the recipe directory.
Resolution
The fix introduces an Assert::pathDoesNotEscapeDirectory() helper that rejects any copy-files source or destination path containing a .. segment, regardless of whether / or \ is used as the separator. This check is enforced in both RecipeManifest (which also guards the source Finder) and File. As a last line of defense, the installer re-verifies the fully resolved paths with Path::isBasePath() immediately before each filesystem read and write.
Credits
Symfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.
Impact
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-55878 has a CVSS score of 7.8 (High). The vector is requires local access, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.36.1, 3.2.0); upgrading removes the vulnerable code path.
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/ux-toolkit to 2.36.1 or later; symfony/ux-toolkit to 3.2.0 or later
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Frequently Asked Questions
- What is CVE-2026-55878? CVE-2026-55878 is a high-severity path traversal vulnerability in symfony/ux-toolkit (composer), affecting versions >= 2.32.0, < 2.36.1. It is fixed in 2.36.1, 3.2.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-55878? CVE-2026-55878 has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of symfony/ux-toolkit are affected by CVE-2026-55878? symfony/ux-toolkit (composer) versions >= 2.32.0, < 2.36.1 is affected.
- Is there a fix for CVE-2026-55878? Yes. CVE-2026-55878 is fixed in 2.36.1, 3.2.0. Upgrade to this version or later.
- Is CVE-2026-55878 exploitable, and should I be worried? Whether CVE-2026-55878 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-2026-55878 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-2026-55878?
- Upgrade
symfony/ux-toolkitto 2.36.1 or later - Upgrade
symfony/ux-toolkitto 3.2.0 or later
- Upgrade