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Fencer Intel
medium 5.1

CVE-2026-42795 json

Symlink Following in Hex Package Export Allows Embedding Files Outside Project Root

published 5mo ago modified last mo. also EUVD-2026-33928

cvss
5.1
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

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.

Patch / fix

  • Gleam Gleam 1.17.0, v1.17.0-elixir, v1.17.0-elixir-alpine, v1.17.0-elixir-slim, v1.17.0-erlang, v1.17.0-erlang-alpine, v1.17.0-erlang-slim, v1.17.0-node, v1.17.0-node-alpine, v1.17.0-node-slim, v1.17.0-scratch
  • gleam openSUSE Leap 16.0 1.17.0-bp160.1.1
  • gleam openSUSE Tumbleweed 1.17.0-1.1

opensuse advisories openSUSE-SU-2026:21143-1openSUSE-SU-2026:10953-1

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
5mo ago

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/gleam-lang/gleam/security/advisories/GHSA-qhh5-fg4c-8gqc referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.1 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
CNA 4.0 5.1 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Gleam Gleam

Classification

Weakness
  • CWE-59 Improper Link Resolution Before File Access

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.