esm.sh writes arbitrary files via path traversal in `X-Zone-Id` header

Vulnerability Description

esm.sh is a nobuild content delivery network(CDN) for modern web development. In 136 and earlier, a path-traversal flaw in the handling of the X-Zone-Id HTTP header allows an attacker to cause the application to write files outside the intended storage location. The header value is used to build a filesystem path but is not properly canonicalized or restricted to the application’s storage base directory. As a result, supplying ../ sequences in X-Zone-Id causes files to be written to arbitrary directories. Version 136.1 contains a patch.

References

• https://github.com/esm-dev/esm.sh/security/advisories/GHSA-g2h5-cvvr-7gmw
• https://github.com/esm-dev/esm.sh/commit/833a29f42aeb0acbd7089a71be11dd0a292d3151
• https://github.com/esm-dev/esm.sh/blob/main/server/router.go#L116
• https://github.com/esm-dev/esm.sh/blob/main/server/router.go#L411