CVE-2026-105274

2.1Low

Published 12 Oct 2026 · NVD status: Deferred · AI triage by gemini-3.8-flash

2.1Low

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Active
Impact: Limited impact
Weakness: CWE-409

Impact

A malicious package repository mirror or rogue upstream API server can crash the Erlang VM running Hex, rebar3, or hex_core via memory exhaustion. The attacker only needs the client to query their server.

Root cause

The client decompresses incoming payloads and decodes terms without bounding their expanded size prior to signature validation and structure verification.

Affected systems

rebar3 3.9.1 before 3.27.3; hex 2.1.0 before 2.5.2; hex_core 0.1.0 before 0.20.0

CVSS v4.0 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:L/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

Fix & remediation

Upgrade hex_core to 0.20.0 or higher, hex to 2.5.2 or higher, and rebar3 to 3.27.3 or higher. If patching must wait, configure clients to only connect to trusted repository mirrors and API endpoints.

shell

$ mix local.hex --force

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

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NVD description

Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex_core allows an untrusted repository mirror, or a server answering hex_core's API requests, to exhaust the memory of the Erlang VM running hex_core. The same code is vendored in Hex (mix_hex_repo, mix_hex_api) and rebar3 (r3_hex_repo, r3_hex_api). hex_repo:get_names/1, hex_repo:get_versions/1, hex_repo:get_package/2 and hex_repo:get_policy/2 decompress the registry response with zlib:gunzip/1 and decode the signed envelope before verifying its signature. A mirror doesn't have the repository's private key, but it chooses the compressed bytes, so a small response decompresses into an envelope of any size before the signature check rejects it. hex_api decodes responses with the application/vnd.hex+erlang content type through hex_safe_binary_to_term:safe_binary_to_term/1, which calls binary_to_term(Binary, [safe]). The safe option prevents atom creation, but it accepts compressed terms and doesn't limit the size of the decoded term, and the check that rejects functions and ports runs after the term has been built. The fix for CVE-2026-21619 added the safe option and that check without bounding the decoded size. This issue affects rebar3: from 3.9.1 before 3.27.3; hex: from 2.1.0 before 2.5.2; hex_core: from 0.1.0 before 0.20.0.

References

Source: nvd.nist.gov/vuln/detail/CVE-2026-105274