CVE-2026-29790 — dbt-common: commonprefix() doesn't protect against path traversal

Affected: dbt-labs dbt-common

dbt-common is the shared common utilities for dbt-core and adapter implementations use. Prior to versions 1.34.2 and 1.37.3, 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. This issue has been patched in versions 1.34.2 and 1.37.3.

GHSA-w75w-9qv4-j5xj — dbt-common's commonprefix() doesn't protect against path traversal

Affected: PyPI: dbt-common

### 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.

### Workaroun…

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CVE-2026-29790 — dbt-common: commonprefix() doesn't protect against path traversal

GHSA-w75w-9qv4-j5xj — dbt-common's commonprefix() doesn't protect against path traversal