CVE-2026-121036
Description
An use after free flaw was found in the CSS component of the Chromium browser.
Upstream bug(s):
Statement
Red Hat Product Security rates the severity of this flaw as determined by the Google Chrome Security Advisory.
Mitigation
--- CME Mitigation Guidance (2026-11-04) ---
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 restrict browser rendering of untrusted web content and enforce renderer sandboxing to contain arbitrary code execution from CSS engine memory corruption: upgrade to Chromium 157.0.8103.38 (or the fixed Chromium builds), which resolves the use-after-free condition during CSS parsing and rendering in the browser engine, closing crafted HTML page with malicious CSS. Until patched, this is a concern on deployments running Chromium where users navigate to or render untrusted web pages, so restrict user browsing to trusted domains and block navigation to unverified external HTML pages. As a compensating measure, enforce ASLR to randomize the Chromium renderer process address space and prevent reliable execution redirection, enable NX/XD bit non-executable memory to prevent execution of payload code placed in heap memory buffers, compile binaries with Full RELRO and PIE to harden position independence and protect relocations from heap corruption, and enforce Control Flow Integrity and Shadow Call Stack to validate indirect call targets and returns against corrupted vtables. These controls limit blast radius and contain exploitation, but they do not fix the underlying use-after-free defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-101 ASLR (Address Space Layout Randomization) (medium)
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
Frequently Asked Questions
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