# CVE-2026-6653: libxml2: Use after free in xmlParseInternalSubset via improper entity resolution handling

> A remote attacker can cause a denial-of-service in libxml2 by sending maliciously crafted XML input that triggers a use-after-free error.

- **Severity:** High 7.0 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Jun 2026
- **Updated:** 22 Jun 2026
- **Also known as:** BELL-CVE-2026-6653, CLSA-2026-1785316608, CLSA-2026-1785317036, CLSA-2026-1785317328, CLSA-2026-1787732374, CLSA-2026-1789473529, DEBIAN-CVE-2026-6653, ECHO-145e-cea4-f440, GHSA-v4qw-p44r-qhfg, JLSEC-2026-1240, RHSA-2026:69655, RLSA-2026:69655, ROOT-OS-DEBIAN-11-CVE-2026-6653, ROOT-OS-DEBIAN-12-CVE-2026-6653, ROOT-OS-DEBIAN-13-CVE-2026-6653, UBUNTU-CVE-2026-6653

## What is CVE-2026-6653?

CVE-2026-6653 is a high-severity use after free vulnerability in Xmlsoft Libxml2, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Use After Free in libxml2's xmlParseInternalSubset from GNOME libxml2 version 2.9.11 to 2.11.0 allows a remote attacker to cause a denial-of-service via maliciously crafted XML input with improper entity resolution handling.

Weakness: CWE-611 (Improper Restriction of XML External Entity Reference), CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-6653?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libxml2-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.9.7-21.el8_10.8 |
| `libxml2-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.9.7-21.el8_10.8 |
| `libxml2-devel` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.9.7-21.el8_10.8 |
| `python3-libxml2-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.9.7-21.el8_10.8 |
| `libxml2` | Red Hat:enterprise_linux:8::baseos | All versions | 0:2.9.7-21.el8_10.8 |
| `libxml2-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:2.9.7-21.el8_10.8 |
| `libxml2-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:2.9.7-21.el8_10.8 |
| `python3-libxml2` | Red Hat:enterprise_linux:8::baseos | All versions | 0:2.9.7-21.el8_10.8 |
| `python3-libxml2-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:2.9.7-21.el8_10.8 |
| `libxml2` | Rocky Linux:8 | All versions | 0:2.9.7-21.el8_10.8 |

Products: Xmlsoft Libxml2.

## How do I fix CVE-2026-6653?

Upgrade to a fixed version.

## Is CVE-2026-6653 being exploited?

There is no known exploitation of CVE-2026-6653 in the wild and no public exploit code.

## Other vulnerabilities in Xmlsoft Libxml2

- [CVE-2017-16931](https://insights.sbomify.com/CVE-2017-16931/): XML external entity in n/a (critical 9.8)
- [CVE-2017-8872](https://insights.sbomify.com/CVE-2017-8872/): Information disclosure in n/a (critical 9.1)
- [CVE-2022-49043](https://insights.sbomify.com/CVE-2022-49043/): Use after free in libxml2 (high 8.1)
- [CVE-2026-86140](https://insights.sbomify.com/CVE-2026-86140/): Memory corruption in libxml2 (high 8.0)
- [CVE-2024-34459](https://insights.sbomify.com/CVE-2024-34459/): Memory corruption in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-6653 and fix it if it is affected.

What it is: CVE-2026-6653 is a high-severity use after free vulnerability in Xmlsoft Libxml2, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-6653 in the wild and no public exploit code.

Affected product: Xmlsoft Libxml2. 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-2026-6653/ (Markdown: https://insights.sbomify.com/CVE-2026-6653/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-6653
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-6653
- OSV: https://osv.dev/vulnerability/CVE-2026-6653

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-6653/
Summaries are generated and may contain mistakes; the official description above is the record.