CVE-2026-33686

A path traversal vulnerability exists in the FileUtil class of the code16/sharp package. The application fails to sanitize file extensions properly, allowing path separators to be passed into the storage layer.

Detail

In src/Utils/FileUtil.php, the FileUtil::explodeExtension() function extracts a file's extension by splitting the filename at the last dot. However, the extracted extension is never sanitized. While the application uses a normalizeName() function, this function only cleans the base filename, meaning any path separators (such as /) injected into the extension will survive and be passed into the storeAs() function.

Credits

Reported by zaurgsynv.

Exploiting this flaw allows an authenticated attacker to manipulate file paths:

• Files can be written outside of the intended tmp directory via path traversal. For more details on the package, visit: https://github.com/code16/sharp
• Existing critical files (such as .env or configuration files) could potentially be overwritten. Review the CWE definition here: https://cwe.mitre.org/data/definitions/22.html (Note: This vulnerability was successfully chained with CWE-434 in a local Proof of Concept to confirm the traversal.)

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-2026-33686 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. 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 (9.20.0); upgrading removes the vulnerable code path.

Kodem intelligence

This issue has been patched by properly sanitizing the extension using pathinfo(PATHINFO_EXTENSION) instead of strrpos(), alongside applying strict regex replacements to both the base name and the extension. The fix is available in pull request #715

1. What is CVE-2026-33686? CVE-2026-33686 is a high-severity path traversal vulnerability in code16/sharp (composer), affecting versions < 9.20.0. It is fixed in 9.20.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-33686? CVE-2026-33686 has a CVSS score of 8.8 (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.
3. Which versions of code16/sharp are affected by CVE-2026-33686? code16/sharp (composer) versions < 9.20.0 is affected.
4. Is there a fix for CVE-2026-33686? Yes. CVE-2026-33686 is fixed in 9.20.0. Upgrade to this version or later.
5. Is CVE-2026-33686 exploitable, and should I be worried? Whether CVE-2026-33686 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
6. What actually determines whether CVE-2026-33686 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.
7. How do I fix CVE-2026-33686? Upgrade code16/sharp to 9.20.0 or later.