# CVE-2026-41240: DOMPurify: FORBID_TAGS bypassed by function-based ADD_TAGS predicate (asymmetry with FORBID_ATTR fix)

> DOMPurify fails to enforce FORBID_TAGS when function-based ADD_TAGS is used, allowing XSS via forbidden elements.

- **Severity:** Medium 6.0 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/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 Apr 2026
- **Updated:** 23 Apr 2026
- **Also known as:** CLEANSTART-2026-PO95463, CLEANSTART-2026-SE92910, DEBIAN-CVE-2026-41240, ECHO-a5a3-4e39-a94b, GHSA-h7mw-gpvr-xq4m, MINI-42pm-x8wv-jhvm, MINI-63v6-83mp-xjjf, MINI-94vc-xm3h-9f6j, MINI-9pcq-w43x-qmc2, MINI-ggq4-hpj5-ff67, MINI-hf94-3pxv-p44m, MINI-jj2w-g8c3-wp74, MINI-jwxq-j82w-c47f, MINI-mrjh-ffc3-43r7, MINI-qqjr-74cc-7wrw, MINI-vfv9-xwcw-p7hj, ROOT-APP-NPM-CVE-2026-41240, UBUNTU-CVE-2026-41240, openSUSE-SU-2026:10888-1

## What is CVE-2026-41240?

CVE-2026-41240 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 23 Apr 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 is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Versions prior to 3.4.0 have an inconsistency between FORBID_TAGS and FORBID_ATTR handling when function-based ADD_TAGS is used. Commit c361baa added an early exit for FORBID_ATTR at line 1214. The same fix was not applied to FORBID_TAGS. At line 1118-1123, when EXTRA_ELEMENT_HANDLING.tagCheck returns true, the short-circuit evaluation skips the FORBID_TAGS check entirely. This allows forbidden elements to survive sanitization with their attributes intact. Version 3.4.0 patches the issue.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-183 (Permissive List of Allowed Inputs)

## Which versions are affected by CVE-2026-41240?

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 |
| `argocd-cli` | openSUSE:Tumbleweed | All versions | 3.4.3-1.1 |

Products: Cure53 Dompurify.

## How do I fix CVE-2026-41240?

Upgrade dompurify to 3.4.0 or later.

## Is CVE-2026-41240 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-41240 exists.

## 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-2026-41240 and fix it if it is affected.

What it is: CVE-2026-41240 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 23 Apr 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-41240 exists.

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-2026-41240/ (Markdown: https://insights.sbomify.com/CVE-2026-41240/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-41240
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41240
- OSV: https://osv.dev/vulnerability/CVE-2026-41240

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-41240/
Summaries are generated and may contain mistakes; the official description above is the record.