# CVE-2025-6497: HTACG tidy-html5 parser.c prvTidyParseNamespace assertion

> A local attacker can trigger a reachable assertion in the tidy-html5 parser, causing a 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:** 23 Jun 2025
- **Updated:** 23 Jun 2025
- **Also known as:** AZL-64317, AZL-64323, DEBIAN-CVE-2025-6497, GHSA-2843-f6r8-wh6v, UBUNTU-CVE-2025-6497

## What is CVE-2025-6497?

CVE-2025-6497 is a medium-severity denial of service vulnerability in HTACG tidy-html5, published on 23 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 HTACG tidy-html5 5.8.0. It has been rated as problematic. This issue affects the function prvTidyParseNamespace of the file src/parser.c. The manipulation leads to reachable assertion. Attacking locally is a requirement. The exploit has been disclosed to the public and may be used.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2025-6497?


## How do I fix CVE-2025-6497?

No fix has been published for CVE-2025-6497 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-6497 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6497 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-6497 and fix it if it is affected.

What it is: CVE-2025-6497 is a medium-severity denial of service vulnerability in HTACG tidy-html5, published on 23 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-2025-6497 exists.

Affected product: HTACG tidy-html5. 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-2025-6497/ (Markdown: https://insights.sbomify.com/CVE-2025-6497/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-6497
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-6497
- OSV: https://osv.dev/vulnerability/CVE-2025-6497

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-6497/
Summaries are generated and may contain mistakes; the official description above is the record.