# CVE-2025-6494: sparklemotion nokogiri hashmap.c hashmap_get_with_hash heap-based overflow

> A heap-based buffer overflow in Nokogiri's Gumbo parser allows local attackers to potentially execute code or cause denial of service.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 22 Jun 2025
- **Updated:** 30 Jun 2025

## What is CVE-2025-6494?

CVE-2025-6494 is a medium-severity memory corruption vulnerability in sparklemotion nokogiri, published on 22 Jun 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability was found in sparklemotion nokogiri c29c920907366cb74af13b4dc2230e9c9e23b833. It has been classified as problematic. This affects the function hashmap_get_with_hash of the file gumbo-parser/src/hashmap.c. The manipulation leads to heap-based buffer overflow. An attack has to be approached locally. The exploit has been disclosed to the public and may be used. The real existence of this vulnerability is still doubted at the moment. The patch is named ada4708e5a67114402cd3feb70a4e1d1d7cf773a. It is recommended to apply a patch to fix this issue. The project maintainer explains that the affected code was merged into the main branch but the commit never appeared in an official release.

Weakness: CWE-122 (Heap-based Buffer Overflow), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2025-6494?


## How do I fix CVE-2025-6494?

No fix has been published for CVE-2025-6494 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-6494 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6494 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-6494 and fix it if it is affected.

What it is: CVE-2025-6494 is a medium-severity memory corruption vulnerability in sparklemotion nokogiri, published on 22 Jun 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6494 exists.

Affected product: sparklemotion nokogiri. 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-2025-6494/ (Markdown: https://insights.sbomify.com/CVE-2025-6494/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-6494
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-6494
- OSV: https://osv.dev/vulnerability/CVE-2025-6494

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-6494/
Summaries are generated and may contain mistakes; the official description above is the record.