CVE-2026-105274 hex_core decompresses registry and Erlang term API responses without size limits
A malicious repository mirror can exhaust Erlang VM memory by sending highly compressed data, causing a denial of service in hex_core, hex, and rebar3.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-105274?
CVE-2026-105274 is a low-severity denial of service vulnerability in erlang hex, published on 12 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-409
Which versions are affected by CVE-2026-105274?
1 open source package ship an affected version, including hex_core.
| Package | Affected | Fixed in |
|---|---|---|
hex_core Hex | From 0.1.0 | 0.20.0 |
How do I fix CVE-2026-105274?
Upgrade hex_core to 0.20.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-105274 being exploited?
There is no known exploitation of CVE-2026-105274 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-105274, EEF-CVE-2026-105274, GHSA-7c4r-cgf9-9jmq, UBUNTU-CVE-2026-105274.