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Review reviewHigh

CVE-2026-59247

gleam-lang gleam

Insufficient Verification of Data Authenticity vulnerability in Gleam allows an adversary in the middle to substitute forged Hex package contents during dependency resolution. During dependency resolution Gleam fetches package metadata from the signature-verified Hex repository, which covers each release's dependency requirements and SHA-256 outer_checksum. After resolving versions, gleam_cli::dependencies::lookup_package makes a second request to the unsigned Hex API through gleam_core::hex::get_package_release and records the outer_checksum and dependency names from that JSON response int...

CVSS
7.6
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.30
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 7.6

Vulnerability overview

Insufficient Verification of Data Authenticity vulnerability in Gleam allows an adversary in the middle to substitute forged Hex package contents during dependency resolution. During dependency resolution Gleam fetches package metadata from the signature-verified Hex repository, which covers each release's dependency requirements and SHA-256 outer_checksum. After resolving versions, gleam_cli::dependencies::lookup_package makes a second request to the unsigned Hex API through gleam_core::hex::get_package_release and records the outer_checksum and dependency names from that JSON response int...

Affected product and versions

Product
gleam-lang gleam
Affected versions
>= 0.18.0 < 1.18.0, >= 8447b78cc844ff4aec44eea23dbd68d1fea11f11 < c9c0d48c123c8abae6db8dd61b25ccb427ed3d35, >= v0.18.0-elixir < v1.18.0-elixir, >= v0.18.0-elixir-slim < v1.18.0-elixir-slim, >= v0.18.0-elixir-alpine < v1.18.0-elixir-alpine, >= v0.18.0-erlang < v1.18.0-erlang, >= v0.18.0-erlang-slim < v1.18.0-erlang-slim, >= v0.18.0-erlang-alpine < v1.18.0-erlang-alpine, >= v0.18.0-node < v1.18.0-node, >= v0.18.0-node-slim < v1.18.0-node-slim, >= v0.18.0-node-alpine < v1.18.0-node-alpine, >= v1.6.0-scratch < v1.18.0-scratch
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that gleam-lang gleam and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/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
CWE
CWE-345
CVE-2026-59247 — gleam-lang gleam | SECUFOCUS NOW