dbt-common's commonprefix() doesn't protect against path traversal

Impact

What kind of vulnerability is it? Who is impacted?

A path traversal vulnerability exists in dbt-common's safe_extract() function used when extracting tarball archives. The function uses os.path.commonprefix() to validate that extracted files remain within the intended destination directory. However, commonprefix() compares paths character-by-character rather than by path components, allowing a malicious tarball to write files to sibling directories with matching name prefixes.

For example, when extracting to /tmp/packages, a crafted tarball could write files to /tmp/packagesevil/ by exploiting the character-based prefix matching.

This vulnerability affects users who:

• Install dbt packages from untrusted sources
• Process tarball archives through dbt-common's extraction utilities

The practical risk is limited because:

• Exploitation requires a malicious tarball to be processed
• File writes are restricted to sibling directories with matching prefixes (not arbitrary paths)
• Packages from trusted sources (dbt Hub) are not affected

This is similar to CVE-2026-1703 in pip, which had a CVSS score of 3.9 (Low).

Patches

Has the problem been patched? What versions should users upgrade to?

Fixed in dbt-common version 1.37.3 & 1.34.2, and patched for dbt-core 1.11.7 and 1.10.20 releases.

The fix replaces os.path.commonprefix() with os.path.commonpath(), which correctly compares paths by their components rather than characters.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

• Only install dbt packages from trusted sources (official dbt Hub, verified git repositories)
• Avoid installing packages from untrusted URLs or unverified third parties
• Review package contents before installation when sourcing from external locations

Resources

Are there any links users can visit to find out more?

1. CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'): https://cwe.mitre.org/data/definitions/22.html
2. CVE-2026-1703 (similar vulnerability in pip): https://nvd.nist.gov/vuln/detail/CVE-2026-1703
3. pip fix PR #13777: https://github.com/pypa/pip/pull/13777
4. Python documentation on commonpath vs commonprefix: https://docs.python.org/3/library/os.path.html#os.path.commonpath