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Gleam vulnerability

Improper path validation vulnerability in the Gleam compiler's handling of git dependencies allows arbitrary file system modification during dependency download. Dependency names from gleam.toml and manifest.toml are incorporated into filesystem paths without sufficient validation or confinement to the intended dependency directory, allowing attacker-controlled paths (via relative traversal such as ../ or absolute paths) to target filesystem locations outside that directory. When resolving git dependencies (e.g. via gleam deps download), the computed path is used for filesystem operations including directory deletion and creation. This vulnerability occurs during the dependency resolution and download phase, which is generally expected to be limited to fetching and preparing dependencies within a confined directory. A malicious direct or transitive git dependency can exploit this issue to delete and overwrite arbitrary directories outside the intended dependency directory, including attacker-chosen absolute paths, potentially causing data loss. In some environments, this may be further leveraged to achieve code execution, for example by overwriting git hooks or shell configuration files. This issue affects Gleam from 1.9.0-rc1 until 1.15.4.

Published 11 Apr 2026Updated 7 Sep 20269 sources
CVSS 8.3 ✓ VERIFIED REFERENCE
Overview Sources History

What happened

Improper path validation vulnerability in the Gleam compiler's handling of git dependencies allows arbitrary file system modification during dependency download. Dependency names from gleam.toml and manifest.toml are incorporated into filesystem paths without sufficient validation or confinement to the intended dependency directory, allowing attacker-controlled paths (via relative traversal such as ../ or absolute paths) to target filesystem locations outside that directory. When resolving git dependencies (e.g. via gleam deps download), the computed path is used for filesystem operations including directory deletion and creation. This vulnerability occurs during the dependency resolution and download phase, which is generally expected to be limited to fetching and preparing dependencies within a confined directory. A malicious direct or transitive git dependency can exploit this issue to delete and overwrite arbitrary directories outside the intended dependency directory, including attacker-chosen absolute paths, potentially causing data loss. In some environments, this may be further leveraged to achieve code execution, for example by overwriting git hooks or shell configuration files. This issue affects Gleam from 1.9.0-rc1 until 1.15.4.

Affected versions

Gleam: 1.9.0-rc1 through before * (semver); a4fde22445ab8e5cc79c2ff48971616cb570702c through before * (git); v1.9.0-rc1-elixir through before v1.15.4-elixir (other); v1.9.0-rc1-erlang through before v1.15.4-erlang (other); v1.9.0-rc1-node through before v1.15.4-node (other); v1.9.0-rc1-node-slim through before v1.15.4-node-slim (other); v1.9.0-rc1-elixir-slim through before v1.15.4-elixir-slim (other); v1.9.0-rc1-erlang-slim through before v1.15.4-erlang-slim (other); v1.9.0-rc1-erlang-alpine through before v1.15.4-erlang-alpine (other); v1.9.0-rc1-elixir-alpine through before v1.15.4-elixir-alpine (other); v1.9.0-rc1-node-alpine through before v1.15.4-node-alpine (other); v1.9.0-rc1-scratch through before v1.15.4-scratch (other) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

  • Apply vendor-provided updates or mitigations.
  • Review affected product exposure and access logs.

Public PoC references

RepositoryAuthorFirst seenReference
github.comNVD reference2026-04-11Verified
CorrectionsReport an issue