CVE-2026-123202
Description
A flaw was found in libnxml. This vulnerability allows a remote attacker to cause a Denial of Service (DoS) by crashing applications that process untrusted data. By supplying specially crafted XML or RSS feeds containing excessively long names ending in multi-byte characters, an attacker can trigger a stack-based buffer overflow in the parser component, leading to an application crash.
Statement
This vulnerability is rated as an Important severity flaw because an unauthenticated remote attacker can cause a denial of service by triggering an application crash without requiring user interaction. Applications consuming untrusted XML feeds or documents via this parser library can be terminated unexpectedly when processing specially crafted input. While stack corruption occurs, the primary demonstrated impact is denial of service against services that process untrusted network inputs.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to prevent multi-byte UTF-8 writes past the 1024-byte stack buffer during XML and RSS name parsing in libnxml: upgrade to libnxml 0.18.6+, which verify that the current index plus incoming multi-byte character length is strictly less than buffer size, closing all 4 injection vectors (crafted XML element names, crafted XML attribute names, crafted DOCTYPE names, crafted XML entity names). Until patched, this is a concern on applications using libnxml to parse untrusted XML documents or RSS feeds, so restrict or filter untrusted XML and RSS feeds before passing them to libnxml parser components. These controls limit blast radius and contain exploitation, but they do not fix the underlying stack-based buffer overflow defect — apply the upstream patch to fully remediate.
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
Frequently Asked Questions
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