# CVE-2026-65903: DOMPurify before 3.4.0 ADD_TAGS Function Bypasses FORBID_TAGS

> Attackers can bypass DOMPurify's FORBID_TAGS restrictions by using ADD_TAGS, allowing forbidden HTML tags to remain in sanitized output.

- **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:** 23 Jul 2026
- **Also known as:** CLEANSTART-2026-BG16749, CLSA-2026-1784596278, CLSA-2026-1784596303, DEBIAN-CVE-2026-65903, ECHO-c3eb-b997-34cf, GHSA-39q2-94rc-95cp, MINI-37xj-25wh-7wvm, MINI-6648-g9jp-49qr, MINI-686v-p2q2-6jhc, MINI-78h6-9mv2-f3cq, MINI-857x-34p7-5j64, MINI-9wch-cw6w-gx8x, MINI-f67j-6hqh-gfgj, MINI-gh5h-3gvr-cf97, MINI-v3m4-4p97-62qx, MINI-vhp3-w6pw-393q, MINI-wm7h-vppp-gw4x, ROOT-APP-NPM-CVE-2026-65903, ROOT-APP-NPM-GHSA-39q2-94rc-95cp, UBUNTU-CVE-2026-65903

## What is CVE-2026-65903?

CVE-2026-65903 is a medium-severity 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

DOMPurify before 3.4.0 contains a logic error in the ADD_TAGS function where short-circuit evaluation allows forbidden tags to bypass FORBID_TAGS restrictions. Attackers can craft input containing tags listed in FORBID_TAGS that are also added via ADD_TAGS function, causing them to be retained in sanitized output.

Weakness: CWE-697 (Incorrect Comparison)

## Which versions are affected by CVE-2026-65903?

2 open source packages ship an affected version, including dompurify. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `dompurify` | npm | All versions | 3.4.0 |
| `dompurify` | npm | All versions | 3.4.0 |

Products: Cure53 Dompurify.

## How do I fix CVE-2026-65903?

Upgrade dompurify to 3.4.0 or later.

## Is CVE-2026-65903 being exploited?

There is no known exploitation of CVE-2026-65903 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-2026-65903 and fix it if it is affected.

What it is: CVE-2026-65903 is a medium-severity 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-2026-65903 in the wild and no public exploit code.

Affected packages and fixed versions:
- dompurify (npm): affected all versions; fixed in 3.4.0
- dompurify (npm): affected all versions; fixed in 3.4.0

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-2026-65903/ (Markdown: https://insights.sbomify.com/CVE-2026-65903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-65903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-65903
- OSV: https://osv.dev/vulnerability/CVE-2026-65903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-65903/
Summaries are generated and may contain mistakes; the official description above is the record.