# CVE-2026-23940: Denial of Service via Oversized Package Upload

> Attackers can cause denial of service on Hex.pm by uploading oversized packages that exhaust server memory during extraction.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Mar 2026
- **Updated:** 8 Sep 2026
- **Also known as:** EEF-CVE-2026-23940, GHSA-jp8w-gxf6-8hcr

## What is CVE-2026-23940?

CVE-2026-23940 is a high-severity denial of service vulnerability in hexpm, published on 13 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Uncontrolled Resource Consumption vulnerability in hexpm hexpm/hexpm allows Excessive Allocation.

Publishing an oversized package can cause Hex.pm to run out of memory while extracting the uploaded package tarball. This can terminate the affected application instance and result in a denial of service for package publishing and potentially other package-processing functionality.

This issue affects hex.pm: before 2026-03-10.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-23940?

It affects 1 product.


Products: Hex Hexpm.

## How do I fix CVE-2026-23940?

No fix has been published for CVE-2026-23940 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-23940 being exploited?

There is no known exploitation of CVE-2026-23940 in the wild and no public exploit code.

## Other vulnerabilities in hexpm

- [CVE-2026-21622](https://insights.sbomify.com/CVE-2026-21622/): Password Reset Tokens Do Not Expire (critical 9.5)
- [CVE-2026-21618](https://insights.sbomify.com/CVE-2026-21618/): Cross-site scripting (XSS) in OAuth Device Authorization screen (high 8.5)
- [CVE-2026-21621](https://insights.sbomify.com/CVE-2026-21621/): Improper Scope Enforcement in OAuth client_credentials Flow Allows Read-Only API Key to Escalate to Full Access (high 7.0)
- [CVE-2026-23939](https://insights.sbomify.com/CVE-2026-23939/): Path Traversal in Local File Store Backend (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23940 and fix it if it is affected.

What it is: CVE-2026-23940 is a high-severity denial of service vulnerability in hexpm, published on 13 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23940 in the wild and no public exploit code.

Affected product: hexpm. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-23940/ (Markdown: https://insights.sbomify.com/CVE-2026-23940/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23940
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23940
- OSV: https://osv.dev/vulnerability/CVE-2026-23940

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23940/
Summaries are generated and may contain mistakes; the official description above is the record.