CVE-2026-117906
Description
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the CSS Parsing and Computation component
Statement
Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Mitigation
--- CME Mitigation Guidance (2026-11-03) ---
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 use-after-free conditions in the CSS parsing and computation engine by validating object lifecycles during style computation: upgrade to Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which remediates memory management handling to eliminate the use-after-free condition during CSS parsing and computation, closing all 2 injection vectors (crafted web page with malicious CSS, crafted HTML email rendering malicious CSS). Until patched, this is a concern on Users processing untrusted web content or HTML emails on any platform, so Avoid opening untrusted links or documents and restrict rendering of untrusted HTML emails with remote CSS. As a compensating measure, Enable Address Space Layout Randomization to randomize process memory and hinder predictable heap exploitation. These controls limit blast radius and contain exploitation, but they do not fix the underlying CSS parsing use-after-free defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-101 ASLR (Address Space Layout Randomization) (medium)
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 6.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | Low |
| Integrity Impact | High | N/A | Low |
| Availability Impact | High | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
Frequently Asked Questions
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