# CVE-2026-45066: Symfony has an HtmlSanitizer allowLinkHosts() / allowMediaHosts() Bypass via URL-Parser Differentials and <area> Misclassification

> Attackers can bypass Symfony HtmlSanitizer host allowlists via URL parsing differences and area tag misclassification, allowing off-allowlist links.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/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:** 14 Jul 2026
- **Updated:** 16 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-45066, GHSA-qc95-4862-92fh, UBUNTU-CVE-2026-45066

## What is CVE-2026-45066?

CVE-2026-45066 is a low-severity vulnerability in Sensiolabs Symfony, published on 14 Jul 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

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 6.1.0-BETA1 until 6.4.40, 7.4.12, and 8.0.12, HtmlSanitizer URL sanitization can allow off-allowlist URLs through allowLinkHosts() or allowMediaHosts() because UrlSanitizer::parse() follows RFC 3986 while browsers follow WHATWG URL parsing, and because <area href> is checked against the media policy rather than the link policy. This issue is fixed in versions 6.4.40, 7.4.12, and 8.0.12.

Weakness: CWE-436 (Interpretation Conflict), CWE-184 (Incomplete List of Disallowed Inputs)

## Which versions are affected by CVE-2026-45066?

12 open source packages ship an affected version, including symfony/html-sanitizer and symfony/symfony. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `symfony/html-sanitizer` | Packagist | From 6.1.0 | 6.4.40 |
| `symfony/html-sanitizer` | Packagist | From 6.1.0 | 6.4.40 |
| `symfony/html-sanitizer` | Packagist | From 7.0.0 | 7.4.12 |
| `symfony/html-sanitizer` | Packagist | From 7.0.0 | 7.4.12 |
| `symfony/html-sanitizer` | Packagist | From 8.0.0 | 8.0.12 |
| `symfony/html-sanitizer` | Packagist | From 8.0.0 | 8.0.12 |
| `symfony/symfony` | Packagist | From 6.1.0 | 6.4.40 |
| `symfony/symfony` | Packagist | From 6.1.0 | 6.4.40 |
| `symfony/symfony` | Packagist | From 7.0.0 | 7.4.12 |
| `symfony/symfony` | Packagist | From 7.0.0 | 7.4.12 |
| `symfony/symfony` | Packagist | From 8.0.0 | 8.0.12 |
| `symfony/symfony` | Packagist | From 8.0.0 | 8.0.12 |

Products: Sensiolabs Symfony.

## How do I fix CVE-2026-45066?

Upgrade symfony/html-sanitizer to a fixed version for your release line: 6.4.40, 7.4.12 or 8.0.12.

## Is CVE-2026-45066 being exploited?

There is no known exploitation of CVE-2026-45066 in the wild and no public exploit code.

## Other vulnerabilities in Sensiolabs Symfony

- [CVE-2019-11325](https://insights.sbomify.com/CVE-2019-11325/): Improper Input Validation in Symfony (critical 9.8)
- [CVE-2017-11365](https://insights.sbomify.com/CVE-2017-11365/): Symfony Incorrect Access Control (critical 9.8)
- [CVE-2019-10913](https://insights.sbomify.com/CVE-2019-10913/): Invalid HTTP method overrides allow possible XSS or other attacks in Symfony (critical 9.8)
- [CVE-2018-11407](https://insights.sbomify.com/CVE-2018-11407/): Symfony Authentication Bypass (critical 9.8)
- [CVE-2016-2403](https://insights.sbomify.com/CVE-2016-2403/): Symfony Authentication Bypass (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45066 and fix it if it is affected.

What it is: CVE-2026-45066 is a low-severity vulnerability in Sensiolabs Symfony, published on 14 Jul 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-2026-45066 in the wild and no public exploit code.

Affected packages and fixed versions:
- symfony/html-sanitizer (Packagist): affected from 6.1.0; fixed in 6.4.40
- symfony/html-sanitizer (Packagist): affected from 6.1.0; fixed in 6.4.40
- symfony/html-sanitizer (Packagist): affected from 7.0.0; fixed in 7.4.12
- symfony/html-sanitizer (Packagist): affected from 7.0.0; fixed in 7.4.12
- symfony/html-sanitizer (Packagist): affected from 8.0.0; fixed in 8.0.12
- symfony/html-sanitizer (Packagist): affected from 8.0.0; fixed in 8.0.12
- symfony/symfony (Packagist): affected from 6.1.0; fixed in 6.4.40
- symfony/symfony (Packagist): affected from 6.1.0; fixed in 6.4.40
- symfony/symfony (Packagist): affected from 7.0.0; fixed in 7.4.12
- symfony/symfony (Packagist): affected from 7.0.0; fixed in 7.4.12
- symfony/symfony (Packagist): affected from 8.0.0; fixed in 8.0.12
- symfony/symfony (Packagist): affected from 8.0.0; fixed in 8.0.12

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-2026-45066/ (Markdown: https://insights.sbomify.com/CVE-2026-45066/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45066
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45066
- OSV: https://osv.dev/vulnerability/CVE-2026-45066

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45066/
Summaries are generated and may contain mistakes; the official description above is the record.