---
id: "CVE-2026-123202"
kind: "vulnerability"
aliases: ["CVE-2026-123202"]
title: "libnxml: long XML names overflow stack buffer, letting remote feeds crash parsers"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["c", "libnxml", "package", "rss", "xml"]
not_affected_if: ["libnxml-not-used", "trusted-input-only"]
published_at: "2026-11-05T19:17:19+00:00"
first_seen_at: "2026-11-05T19:40:36+00:00"
updated_at: "2026-11-05T19:42:40+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123202", "first_seen_at": "2026-11-05T19:40:36+00:00"}]
exploit_sources: []
---

# libnxml: long XML names overflow stack buffer, letting remote feeds crash parsers

libnxml is a C library for parsing XML. A crafted XML or RSS feed with a very long element, attribute, DOCTYPE or entity name overflows a 1024-byte stack buffer, and the sources say this crashes the parsing application.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Look for libnxml in your dependencies or build files, for example `pkg-config --modversion nxml` or the libnxml line in your package manifest.
- Check whether the installed version is below `0.18.6`.
- Note whether your application parses untrusted XML or RSS feeds with libnxml.

## Fix

- libnxml: move to `0.18.6` or later (the sources name the fix as the release that patches the flaw).

## Timeline

- 2026-11-05T19:40:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123202

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/libnxml-before-0.18.6-stack-based-buffer-overflow-via-long-multi-byte-xml-name
- [fix] Patch: github.com https://github.com/bakulf/libnxml/commit/fbac242374883edf2ec14127ca6d2accf4704b6a
- [fix] Release notes: github.com https://github.com/bakulf/libnxml/releases/tag/0.18.6

## From the sources

libnxml before 0.18.6 contains a stack-based buffer overflow vulnerability in src/nxml_parser.c that allows remote attackers to write past a 1024-byte stack buffer via long XML names. Attackers can supply XML or RSS feeds with a 1022-character element, attribute, DOCTYPE or entity name ending in a multi-byte UTF-8 character to crash parsing applications.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_