CVE-2026-43965: Gleam

Medium severity, CVSS 5.6. EPSS: 0.2% chance of exploitation in the next 30 days.

Path traversal vulnerability in Gleam's dependency management allows arbitrary directory deletion via malicious build/packages/packages.toml content. Package keys read from build/packages/packages.toml by LocalPackages::read_from_disc are passed without validation to paths.build_packages_package(), which constructs a filesystem path by joining the project build directory with the attacker-controlled key. The resulting path is then passed to fs::delete_directory (which calls remove_dir_all). No check is performed to ensure the path remains within the intended build/packages/ directory. Both absolute paths and relative traversal sequences (e.g. ../) are accepted as package keys, allowing deletion of arbitrary directories. An attacker who can cause a victim to run gleam deps download on a project containing a malicious build/packages/packages.toml (e.g. by committing the normally-gitignored file to a repository) can cause arbitrary directories on the victim's system to be recursively deleted. This issue affects Gleam from 0.18.0-rc1 until 1.17.0.

Affected products

• Gleam Gleam: from 0.18.0-rc1, before 1.17.0 (fixed in 1.17.0); from v0.18.0-rc1-elixir, before v1.17.0-elixir (fixed in v1.17.0-elixir); from v0.18.0-rc1-erlang, before v1.17.0-erlang (fixed in v1.17.0-erlang); from v0.18.0-rc1-node, before v1.17.0-node (fixed in v1.17.0-node); from v0.18.0-rc1-node-slim, before v1.17.0-node-slim (fixed in v1.17.0-node-slim); from v0.18.0-rc1-elixir-slim, before v1.17.0-elixir-slim (fixed in v1.17.0-elixir-slim); …

Published 2026-06-02. Last modified 2026-10-06.