CVE-2025-6424VulnerabilityPublished 1 Jul 2025Updated 28 Jun 2026

Red Hat Security Advisory: firefox security update

Affects Red Hat firefoxSource GCVE Database

Mentioned vulnerabilities

Authoritative record:CVE-2025-6424· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical : upgrade the Red Hat redhat/firefox package to 9 as a priority.

Data as of 26 Oct 2026, 09:16 UTC

CVSS 3.1 base score

9.8Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 7.9% chance of exploitation in 30 days – higher than 94% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade the Red Hat redhat/firefox package to 9.

Affected software

Product	Affected	Fixed in
Red Hatredhat/firefox`pkg:rpm/redhat/firefox`Other threats	Affected =8.* <9	Fixed in 9

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AI-suggested

Red Hat has released updated Firefox packages that address these vulnerabilities. Users and administrators should apply the Firefox update (version 128.12.0-1.el8_10) available through Red Hat Enterprise Linux 8 and Extended Life Cycle 8.10 repositories as soon as possible. For detailed update instructions, refer to Red Hat's official article at https://access.redhat.com/articles/11258. No additional mitigations are indicated by the vendor advisory.

Description

Mozilla Firefox is an open-source web browser, designed for standards compliance, performance, and portability. Security Fix(es): * firefox: Content-Disposition header ignored when a file is included in an embed or object tag (CVE-2025-6430) * firefox: Use-after-free in FontFaceSet (CVE-2025-6424) * firefox: Incorrect parsing of URLs could have allowed embedding of youtube.com (CVE-2025-6429) * firefox: The WebCompat WebExtension shipped with Firefox exposed a persistent UUID (CVE-2025-6425) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Impact

The vulnerabilities fixed include a use-after-free condition that could lead to memory corruption, improper handling of HTTP headers affecting content embedding, incorrect URL parsing that could allow unauthorized embedding of external content, and exposure of a persistent UUID that may impact user privacy. These issues collectively could affect browser stability, security, and user privacy on affected Red Hat Enterprise Linux 8 systems running Firefox.

Summary

Red Hat Product Security released an advisory (RHSA-2025:10074) for Mozilla Firefox on Red Hat Enterprise Linux 8, addressing four security vulnerabilities: CVE-2025-6424 (use-after-free in FontFaceSet), CVE-2025-6430 (Content-Disposition header ignored in embed/object tags), CVE-2025-6429 (incorrect URL parsing enabling embedding of youtube.com), and CVE-2025-6425 (persistent UUID exposure in WebCompat WebExtension). These vulnerabilities impact Firefox's handling of web content and extensions, potentially leading to memory corruption and privacy issues. The advisory provides updated Firefox packages (version 128.12.0-1.el8_10) for multiple architectures including x86_64, s390x, ppc64le, and aarch64. No CVSS scores were provided in the advisory. The update is classified as Important by Red Hat and is available for installation.

CWE-416Use After Free (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #7
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Architecture and Design · Language Selection
Choose a language that provides automatic memory management.
Implementation · Attack Surface Reduction
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-200Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #20OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Subverting Environment Variable Values (opens in a new tab)
ICMP Echo Request Ping (opens in a new tab)
TCP SYN Scan (opens in a new tab)
Enumerate Mail Exchange (MX) Records (opens in a new tab)
DNS Zone Transfers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-706Use of Incorrectly-Resolved Name or Reference (opens in a new tab)
Class weaknessOWASP Top 10 A01:2021: Broken Access Control (opens in a new tab)
The product uses a name or reference to access a resource, but the name/reference resolves to a resource that is outside of the intended control sphere.
Attack patterns
Redirect Access to Libraries (opens in a new tab)
Create files with the same name as files protected with a higher classification (opens in a new tab)
Passing Local Filenames to Functions That Expect a URL (opens in a new tab)
DLL Side-Loading (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Jun 2026, 06:46 UTC

WeaknessesCWE-416, CWE-200, CWE-706 +1

Technical details

References

Community reviews

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