CVE-2026-42795

Summary

Symlink following vulnerability in Gleam's Hex package export allows files outside the project root to be embedded in the generated package tarball.

The file collection helpers (gleam_files, native_files, private_files) in compiler-cli/src/fs.rs use follow_links(true) when walking publishable directories such as src/ and priv/. The collected paths are added to the package archive via add_path_to_tar in compiler-cli/src/publish.rs without verifying that the resolved target remains within the project root. A symlink placed under a publishable directory will cause gleam export hex-tarball or gleam publish to embed the contents of the symlink target into the generated Hex package.

An attacker with write access to the project repository can place a symlink in src/ or priv/ pointing to an arbitrary file. When a maintainer or CI pipeline runs gleam publish or gleam export hex-tarball, local files readable by the publisher (such as secrets, tokens, or SSH keys) are silently embedded into the published package artifact.

This issue affects Gleam from 0.10.0-rc1 until 1.17.0.

Affected Software

Weaknesses

• CWE-59: CWE-59 Improper Link Resolution Before File Access ('Link Following')

Workarounds

• Avoid running gleam publish or gleam export hex-tarball on untrusted projects
• Review the contents of src/ and priv/ for unexpected symlinks before publishing
• Run publishing commands in a restricted or isolated environment (e.g. containers)

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: poc
  • Automatable: no
  • Technical Impact: partial

Additional References

• https://github.com/gleam-lang/gleam/security/advisories/GHSA-qhh5-fg4c-8gqc

References

• https://github.com/gleam-lang/gleam/security/advisories/GHSA-qhh5-fg4c-8gqc
• https://cna.erlef.org/cves/CVE-2026-42795.html
• https://osv.dev/vulnerability/EEF-CVE-2026-42795
• https://github.com/gleam-lang/gleam/commit/6435a5528b9ae0449e2f32be579641ec485f6866

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