# CVE-2026-65911: DOMPurify before 3.4.0 XSS via ADD_ATTR/ADD_TAGS State Leakage

> State leakage in DOMPurify allows XSS when mixing function and array configurations for ADD_ATTR or ADD_TAGS across sanitize calls.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/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:** 23 Jul 2026
- **Updated:** 27 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-65911, GHSA-9p3w-6h5p-cv75, UBUNTU-CVE-2026-65911

## What is CVE-2026-65911?

CVE-2026-65911 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 23 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

In DOMPurify through 3.3.3, function predicates supplied via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state (EXTRA_ELEMENT_HANDLING) across subsequent sanitize() calls on the same instance. If a later call on the same instance provides ADD_ATTR or ADD_TAGS as an array rather than a function, the previously set function handler is neither cleared nor overwritten, so it continues to approve attacker-controlled attributes or tags. This can allow dangerous event-handler attributes or forbidden tags (bypassing FORBID_TAGS) to survive sanitization, resulting in cross-site scripting. The vendor (Cure53) considers this an edge case outside DOMPurify's threat model; the referenced advisory lists 3.4.0 as the patched version.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-65911?

It affects 1 product.


Products: Cure53 Dompurify.

## How do I fix CVE-2026-65911?

Upgrade to a fixed version.

## Is CVE-2026-65911 being exploited?

There is no known exploitation of CVE-2026-65911 in the wild and no public exploit code.

## Other vulnerabilities in cure53 DOMPurify

- [CVE-2024-47875](https://insights.sbomify.com/CVE-2024-47875/): DOMPurify nesting-based mXSS (critical 10.0)
- [CVE-2024-48910](https://insights.sbomify.com/CVE-2024-48910/): DOMPurify vulnerable to tampering by prototype polution (critical 9.1)
- [CVE-2026-47423](https://insights.sbomify.com/CVE-2026-47423/): DOMPurify XSS via `selectedcontent` re-clone (high 8.2)
- [CVE-2024-45801](https://insights.sbomify.com/CVE-2024-45801/): Tampering by prototype polution in DOMPurify (high 7.3)
- [CVE-2026-49978](https://insights.sbomify.com/CVE-2026-49978/): DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-65911 and fix it if it is affected.

What it is: CVE-2026-65911 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 23 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-2026-65911 in the wild and no public exploit code.

Affected product: cure53 DOMPurify. 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-2026-65911/ (Markdown: https://insights.sbomify.com/CVE-2026-65911/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-65911
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-65911
- OSV: https://osv.dev/vulnerability/CVE-2026-65911

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-65911/
Summaries are generated and may contain mistakes; the official description above is the record.