pybars3 through 0.9.7 Code Injection via Bracketed Path Segments

Summary

pybars3 through 0.9.7 contains a code injection vulnerability in pybars/_compiler.py that allows template authors to execute Python code via unescaped bracketed path segments. Attackers can supply Handlebars templates with crafted segments in helper or block arguments to break out of string literals and execute Python in the application process.

Remediation

1. Inventory every wbond pybars3 deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Advisoryhttps://github.com/vladko312/advisories/blob/702e98db9642ece70d9e2150076d8014ffec2db3/pybars3.md
• Advisoryhttps://www.vulncheck.com/advisories/pybars3-through-0.9.7-code-injection-via-bracketed-path-segments
• Referencehttps://github.com/wbond/pybars3
• Referencehttps://github.com/wbond/pybars3/blob/0.9.7/pybars/_compiler.py#L159-L160
• Referencehttps://github.com/wbond/pybars3/issues/88
• Referencehttps://github.com/up9inc/pybars4
• Referencehttps://github.com/up9inc/pybars4/blob/0.9.13/pybars/_compiler.py#L153-L154