EEF-CVE-2026-47078

Relative path traversal in zip:unzip/zip:extract via check_dir_level depth-counter bypass

## Summary Relative Path Traversal vulnerability in Erlang OTP (stdlib zip module) allows writing files outside the intended extraction directory via a crafted zip archive. `zip:unzip/1,2` and `zip:extract/1,2` validate entry paths using `zip:check_dir_level/2`, which tracks directory depth as a running integer counter: `..` decrements it, normal path components increment it. The caller rejects only paths where the final counter value is less than zero. A path such as `../x/y` causes the counter to go negative mid-traversal then recover to zero, passing validation while resolving to a location outside the extraction directory when joined with the current working directory via `add_cwd`. This vulnerability is associated with program file `lib/stdlib/src/zip.erl`. This issue affects OTP from OTP 27.1 before OTP 27.3.4.15, OTP 28.5.0.4, and OTP 29.0.4, corresponding to stdlib from 6.1 before 6.2.2.4, 7.3.0.1, and 8.0.3.