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Mozilla Firefox CVE-2026-109710

| EUVDEUVD-2026-98636 MEDIUM
Use After Free (CWE-416)
2026-10-13 mozilla GHSA-qq73-8c3h-jgr4
5.4
CVSS 3.1 · Vendor: mozilla
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Lure victim to malicious page
  2. Delivery
    Deliver crafted graphics/text content
  3. Exploit
    Trigger use-after-free in text renderer
  4. Execution
    Read/corrupt freed memory
  5. Impact
    Disclose limited in-process data

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires the victim to actively load attacker-controlled web content in Firefox so the Graphics: Text component renders a malicious payload - the UI:R metric and the rendering component confirm user interaction (visiting a page or opening content) is mandatory; there is no server-side or unauthenticated-daemon exposure. Limiting factors: the attack only affects users on unpatched Firefox prior to 158, ESR before 115.43, or ESR before 153.5, and impact is bounded to limited confidentiality/integrity with no availability effect, likely constrained by browser memory-safety mitigations. No special non-default configuration is required beyond normal web browsing.

Impact

This is a moderate-severity memory-safety issue that does not currently rise to the level of an urgent, must-patch-now priority. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N, base 5.4) describes a network-reachable, low-complexity flaw requiring no privileges but requiring user interaction - consistent with a victim visiting or rendering attacker-controlled web content in Firefox. All signals point the same direction and are mutually consistent: SSVC reports Exploitation 'none', Automatable 'no', and Technical Impact 'partial', which aligns with the limited low/low confidentiality and integrity impact and no availability impact. There is no CISA KEV listing and no public exploit referenced, so exploitation status is 'no public exploit identified at time of analysis'. No EPSS score was provided in the input, so probabilistic exploitation likelihood could not be weighed. The one nuance worth flagging: CWE-416 use-after-free in a graphics/text rendering path is the classic primitive attackers chain toward code execution, yet Mozilla scored impact as only low C/low I with no availability effect - this suggests either mitigations (e.g., site isolation, hardened allocators) constrain the primitive, or the vendor assessed it as an info-leak rather than a reliable RCE. The 'Information Disclosure' tag supports the info-leak reading. Net: a real but routine browser memory-safety bug best handled through normal patch cadence, not emergency response.

Exploit ScenarioDerived

An attacker hosts a malicious web page containing specially crafted graphics/text content and lures a Firefox user to visit it (UI:R). Rendering the content triggers a use-after-free in the Graphics: Text component, allowing the attacker to read small amounts of out-of-bounds memory or corrupt limited process state, consistent with the low confidentiality/integrity impact. No public exploit code was identified, so weaponization effort remains unproven.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 13, 2026

Memory-safety flaws in Mozilla Firefox's Graphics: Text component allow remote attackers who convince a user to load crafted web content to trigger a use-after-free, potentially exposing or corrupting data in the browser's process memory. Impact is bounded to limited confidentiality and integrity effects with no availability loss (CVSS 5.4, C:L/I:L/A:N), and exploitation is limited to unpatched builds (versions before Firefox 158, ESR before 115.43, and ESR before 153.5) that render the malicious payload during normal browsing. No public exploit code has been identified at time of analysis and the CISA SSVC assessment rates exploitation as 'none', making this a moderate memory-safety fix to fold into routine browser patching rather than an emergency action.

RemediationAI

Vendor-released patch: Firefox 158, Firefox ESR 115.43, and Firefox ESR 153.5 - upgrade to the build matching your release channel (mainstream users to 158 or later; ESR administrators must deploy the appropriate ESR build for each branch they run, since updating only 115.43 or only 153.5 leaves the other line exposed). Release details and confirmation of the fix are in the Mozilla advisories at https://www.mozilla.org/security/advisories/mfsa2026-106/, https://www.mozilla.org/security/advisories/mfsa2026-107/, and https://www.mozilla.org/security/advisories/mfsa2026-108/, tracking bug https://bugzilla.mozilla.org/show_bug.cgi?id=2068338. Because this is a memory-safety defect in the text renderer, there is no meaningful configuration toggle, settings change, or feature flag that removes exposure - the text engine is always active - so compensation is limited to exposure reduction rather than a true fix: enforce automatic updates and verify version compliance across managed endpoints, and where immediate patching is impossible, constrain browsing of untrusted content (blocked or allow-listed navigation, isolated/sandboxed browser profiles, or remote browsing through a hardened host). Each of those measures degrades usability and does not eliminate the underlying use-after-free, so they should be treated only as temporary stopgaps until the patched versions are deployed.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This is a CWE-416 use-after-free in the Graphics: Text component, the Gecko subsystem responsible for text shaping, font handling, glyph layout, and rasterization of rendered text. The class of bug arises when an object associated with the text-rendering path (e.g. a font, glyph run, or layout buffer) is freed while a stale reference is still held, so a subsequent render pass dereferences recycled memory - an attacker who controls page content can influence the allocation pattern and potentially reuse the freed region to leak or corrupt data. Consistent with the assessed vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N, the flaw is remotely reachable without credentials (PR:N) but strictly requires the victim to load attacker-controlled content (UI:R), and the CPE key cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* marks the affected product line generically. There is no server-side or daemon exposure, SSVC records the technical impact as partial with automatable exploitation as 'no', and browser memory-safety mitigations (process sandboxing, ASLR, compartmentalization) are the likely reason impact remains confined to limited confidentiality/integrity rather than full code execution.

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Severity by source

Vendor (mozilla) PRIMARY 5.4 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
vuln.today AI 5.4 MEDIUM

Triggered by rendering remote web content, so AV:N/AC:L/PR:N with UI:R for the required page visit; vendor-indicated limited info-leak/corruption yields C:L/I:L and A:N, scope unchanged.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

3
CVSS changed
Oct 13, 2026 - 15:37 NVD
5.4 (None) 5.4 (MEDIUM)
CVE Published
Oct 13, 2026 - 12:29 cve.org
UNKNOWN (no severity yet)
CVE Published
Oct 13, 2026 - 12:29 cve.org
MEDIUM 5.4

DescriptionCVE.org

Use-after-free in the Graphics: Text component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, and Firefox ESR 153.5.

Threat Intelligence Overview

EPSS Score
0.2%
Top 87% exploitable
Prevalence
Ubiquitous
Firefox is one of the most widely deployed desktop web browsers globally
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

27
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +27
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)CVE.org

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
CVE-2013-0758 CRITICAL POC
9.3 Jan 13

Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and 17.x before 17.0.2, Thunderbird before 17.0.2, Thunderb

CVE-2013-0753 CRITICAL POC
9.3 Jan 13

Use-after-free vulnerability in the serializeToStream implementation in the XMLSerializer component in Mozilla Firefox b

CVE-2012-3993 CRITICAL POC
9.3 Oct 10

The Chrome Object Wrapper (COW) implementation in Mozilla Firefox before 16.0, Firefox ESR 10.x before 10.0.8, Thunderbi

CVE-2013-1710 CRITICAL POC
10.0 Aug 07

The crypto.generateCRMFRequest function in Mozilla Firefox before 23.0, Firefox ESR 17.x before 17.0.8, Thunderbird befo

CVE-2014-8636 HIGH POC
7.5 Jan 14

The XrayWrapper implementation in Mozilla Firefox before 35.0 and SeaMonkey before 2.32 does not properly interact with

CVE-2013-0757 CRITICAL POC
9.3 Jan 13

The Chrome Object Wrapper (COW) implementation in Mozilla Firefox before 18.0, Firefox ESR 17.x before 17.0.2, Thunderbi

CVE-2014-1510 CRITICAL POC
9.8 Mar 19

The Web IDL implementation in Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and Se

CVE-2014-1511 CRITICAL POC
9.8 Mar 19

Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and SeaMonkey before 2.25 allow remo

CVE-2016-1960 HIGH POC
8.8 Mar 13

Integer underflow in the nsHtml5TreeBuilder class in the HTML5 string parser in Mozilla Firefox before 45.0 and Firefox

CVE-2015-0816 MEDIUM POC
5.0 Apr 01

Mozilla Firefox before 37.0, Firefox ESR 31.x before 31.6, and Thunderbird before 31.6 do not properly restrict resource

CVE-2015-0802 MEDIUM POC
5.0 Apr 01

Mozilla Firefox before 37.0 relies on docshell type information instead of page principal information for Window.webidl

CVE-2013-2566 MEDIUM POC
5.9 Mar 15

The RC4 algorithm, as used in the TLS protocol and SSL protocol, has many single-byte biases, which makes it easier for

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