# CVE-2011-4838: Denial of service in n/a

> Attackers can cause CPU exhaustion and denial of service in JRuby applications by sending crafted input that triggers predictable hash collisions.

- **Severity:** Medium 5.0 (`AV:N/AC:L/Au:N/C:N/I:N/A:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 30 Dec 2011
- **Updated:** 7 Aug 2024
- **Also known as:** DEBIAN-CVE-2011-4838, GHSA-cgqc-fqxr-q6r6

## What is CVE-2011-4838?

CVE-2011-4838 is a medium-severity denial of service vulnerability in n/a, published on 30 Dec 2011. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

JRuby before 1.6.5.1 computes hash values without restricting the ability to trigger hash collisions predictably, which allows context-dependent attackers to cause a denial of service (CPU consumption) via crafted input to an application that maintains a hash table.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2011-4838?

It affects 1 product.


Products: Jruby Jruby.

## How do I fix CVE-2011-4838?

Upgrade to a fixed version.

## Is CVE-2011-4838 being exploited?

There is no known exploitation of CVE-2011-4838 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2025-46551](https://insights.sbomify.com/CVE-2025-46551/): JRuby-OpenSSL has hostname verification disabled by default (medium 5.7)
- [CVE-2012-5370](https://insights.sbomify.com/CVE-2012-5370/): JRuby denial of service via Hash Collision (medium 5.0)
- [CVE-2010-1330](https://insights.sbomify.com/CVE-2010-1330/): Cross-site Scripting in in JRuby (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2011-4838 and fix it if it is affected.

What it is: CVE-2011-4838 is a medium-severity denial of service vulnerability in n/a, published on 30 Dec 2011. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2011-4838 in the wild and no public exploit code.

Affected product: n/a. 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-2011-4838/ (Markdown: https://insights.sbomify.com/CVE-2011-4838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2011-4838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2011-4838
- OSV: https://osv.dev/vulnerability/CVE-2011-4838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2011-4838/
Summaries are generated and may contain mistakes; the official description above is the record.