# 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.

- **Severity:** Low 2.1 (`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`)
- **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:** Yes
- **Published:** 12 Oct 2026
- **Updated:** 15 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-105274, EEF-CVE-2026-105274, GHSA-7c4r-cgf9-9jmq, UBUNTU-CVE-2026-105274

## 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 (Improper Handling of Highly Compressed Data (Data Amplification))

## Which versions are affected by CVE-2026-105274?

1 open source package ship an affected version, including hex_core.


| Package | Ecosystem | 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.

## Is CVE-2026-105274 being exploited?

There is no known exploitation of CVE-2026-105274 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-105274 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-105274 in the wild and no public exploit code.

Affected packages and fixed versions:
- hex_core (Hex): affected from 0.1.0; fixed in 0.20.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-105274/ (Markdown: https://insights.sbomify.com/CVE-2026-105274/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-105274
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-105274
- OSV: https://osv.dev/vulnerability/CVE-2026-105274

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-105274/
Summaries are generated and may contain mistakes; the official description above is the record.