# CVE-2026-76781: Libxml2: libxml2: null pointer dereference parsing nextcatalog without catalog attribute

> A local attacker can cause a denial of service by providing a crafted XML catalog with a missing attribute, crashing applications using libxml2.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 24 Sep 2026
- **Also known as:** BELL-CVE-2026-76781, DEBIAN-CVE-2026-76781, ECHO-2007-775f-9d2b, GHSA-2j5r-8qjf-mq34, MGASA-2026-0558, RHSA-2026:57604, UBUNTU-CVE-2026-76781

## What is CVE-2026-76781?

CVE-2026-76781 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 17 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

A flaw was found in libxml2. A local user or an attacker providing a specially crafted XML catalog can trigger a NULL pointer dereference during XML catalog parsing. This occurs when a `nextCatalog` element lacks its mandatory `catalog` attribute, leading to the application crashing and causing a Denial of Service (DoS).

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-76781?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libxml2` | Red Hat:hummingbird:1 | All versions | 0:2.15.3-0.1.3.hum1 |
| `libxml2-16` | Red Hat:hummingbird:1 | All versions | 0:2.15.3-0.1.3.hum1 |
| `libxml2-devel` | Red Hat:hummingbird:1 | All versions | 0:2.15.3-0.1.3.hum1 |
| `libxml2-static` | Red Hat:hummingbird:1 | All versions | 0:2.15.3-0.1.3.hum1 |
| `python3-libxml2` | Red Hat:hummingbird:1 | All versions | 0:2.15.3-0.1.3.hum1 |

## How do I fix CVE-2026-76781?

Apply the vendor's patch.

## Is CVE-2026-76781 being exploited?

There is no known exploitation of CVE-2026-76781 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76781 and fix it if it is affected.

What it is: CVE-2026-76781 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 17 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-76781 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. 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-2026-76781/ (Markdown: https://insights.sbomify.com/CVE-2026-76781/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76781
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76781
- OSV: https://osv.dev/vulnerability/CVE-2026-76781

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76781/
Summaries are generated and may contain mistakes; the official description above is the record.