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Mozilla Firefox CVE-2026-100782

| EUVDEUVD-2026-88934 HIGH
Buffer Overflow (CWE-119)
2026-09-29 mozilla GHSA-vw5f-8j4q-78qm
8.8
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
    Host malicious graphics content on web page
  2. Delivery
    Lure victim to load page in Firefox
  3. Exploit
    Trigger incorrect boundary condition in Graphics component
  4. Execution
    Corrupt content-process memory
  5. Impact
    Execute code with process privileges

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, buffer size validation
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 load attacker-controlled content that exercises the vulnerable Graphics-component code path in Firefox (UI:R - user must open a crafted page or content). No authentication is required (PR:N) and no special non-default configuration is named in the description; standard Firefox with graphics rendering active is sufficient. The primary limiting factors are the mandatory user interaction (defeating automated/wormable spread, consistent with SSVC Automatable:no) and that only unpatched builds below Firefox 157 / ESR 153.4 / ESR 140.17 / ESR 115.42 are affected - updating to these versions fully remediates.

Impact

This is a genuine but not top-priority issue. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H = 8.8 High) describes a network-reachable, low-complexity, unauthenticated memory-corruption flaw (CWE-119 incorrect boundary conditions in the Graphics component) that nonetheless requires user interaction (UI:R) - the victim must load attacker-controlled content in Firefox. CISA SSVC reinforces a measured posture: Exploitation is rated 'none' (no observed or public exploitation), Automatable 'no' (the UI:R requirement defeats mass/wormable automation), while Technical Impact is 'total' (full compromise of the content process if triggered). No EPSS score, no CISA KEV listing, and no public POC are present in the input, so exploitation status is: no public exploit identified at time of analysis. The signals are internally consistent - a serious memory-safety bug with high technical impact but no evidence of real-world weaponization, disclosed and fixed by the vendor as part of a coordinated Mozilla release batch (MFSA2026-97 through -100). One label tension: the CVE is tagged 'Privilege Escalation' and the description says 'Privilege escalation,' but S:U (scope unchanged) plus CWE-119 indicates in-process memory corruption rather than a scope-changing sandbox escape; treat the 'privilege escalation' phrasing as Mozilla's classification for an exploitable memory-safety bug, not a confirmed host-level escape. Net: patch on the normal browser update cycle; this is not a drop-everything emergency but should not be deferred given ubiquitous deployment.

Exploit ScenarioDerived

An attacker hosts a malicious web page (or serves malicious ad/embedded content) that triggers the incorrect boundary condition in Firefox's Graphics component when rendered. A victim running an unpatched Firefox/ESR build visits the page (UI:R satisfied), the boundary error corrupts memory in the content process, and the attacker gains code execution with the impacted process's privileges. No public exploit code is identified at time of analysis, and CISA SSVC rates exploitation as 'none.'

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 29, 2026

Boundary-condition errors in Mozilla Firefox's Graphics component allow an unauthenticated remote attacker to trigger memory corruption and achieve privilege escalation on the affected platform, provided the victim loads attacker-controlled content that reaches the vulnerable rendering code path. Only builds below Firefox 157, Firefox ESR 153.4, Firefox ESR 140.17, and Firefox ESR 115.42 are affected - updating to any of those versions fully remediates the issue. Although the CVSS base score is 8.8 with high confidentiality, integrity, and availability impact, no public exploit code has been identified at time of analysis, CISA's SSVC assessment rates exploitation as 'none' and the flaw as not automatable, and the mandatory user-interaction requirement (UI:R) prevents automated or wormable spread, making this a genuine but not top-priority issue.

RemediationAI

Vendor-released patch: upgrade to Mozilla Firefox 157 or, for extended-support deployments, to Firefox ESR 153.4, Firefox ESR 140.17, or Firefox ESR 115.42 - any one of these versions remediates CVE-2026-100782, and there is no backport available for older ESR lines beyond their stated fix versions. Prioritize this update on systems where the browser processes untrusted web content, but note that the requirement for user interaction (victim must load attacker-controlled content) means this is not an emergency, out-of-band change for most environments. Because no non-browser workaround is documented by Mozilla and the bug is in the graphics rendering path, compensating controls are limited and carry trade-offs: disabling hardware/GPU acceleration or WebGL may reduce exposure to the affected rendering routine but can degrade performance and break legitimate sites and is not a vendor-confirmed mitigation, and blocking untrusted or unknown content via proxy/web-filtering or enterprise policy reduces the chance of the victim reaching a crafted page at the cost of restricting browsing. The authoritative remediation guidance is the Mozilla advisory set (https://www.mozilla.org/security/advisories/mfsa2026-97/, mfsa2026-98, mfsa2026-99, mfsa2026-100) and the Bugzilla record at https://bugzilla.mozilla.org/show_bug.cgi?id=2068456.

Affects your stack

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

Technical ContextAI · show details

The flaw is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), the classic memory-safety class covering out-of-bounds reads and writes, and is rooted in incorrect boundary checks inside Firefox's Graphics component - the rendering subsystem responsible for compositing, image decoding, and GPU-accelerated drawing paths. Because the erroneous bounds validation sits in the graphics pipeline, crafted web content that drives the affected rendering routine can corrupt memory, and the attacker can then pivot that corruption into code execution with the privileges of the browser process, satisfying the integrity, confidentiality, and availability impact ratings. The CPE record (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) confirms the affected product line is Mozilla Firefox across all release channels and ESR branches predating the fixed versions, and the referenced Bugzilla entry (bug 2068456) plus the four Mozilla Foundation Security Advisories (mfsa2026-97 through mfsa2026-100) document the fix landing in Firefox 157, Firefox ESR 153.4, Firefox ESR 140.17, and Firefox ESR 115.42. The CVSS vector AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H indicates a remote, unauthenticated attack that requires the victim to interact with attacker-supplied content; the single-scope rating (S:U) means the exploit does not cross a security boundary within Mozilla's own scoring model, but the high C/I/A subscores reflect total technical impact once the vulnerable code path is exercised. ENISA tracks the issue as EUVD-2026-88934.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (mozilla) PRIMARY 8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
vuln.today AI 8.8 HIGH

Network-delivered crafted content, no auth, but requires the victim to load the page (UI:R); memory corruption yields full content-process compromise (C/I/A:H) with scope unchanged (S:U).

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Red Hat 7.5 HIGH

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

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

Lifecycle Timeline

2
CVE Published
Sep 29, 2026 - 12:36 cve.org
HIGH 8.8
CVE Published
Sep 29, 2026 - 12:36 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Privilege escalation due to incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Executive ViewAI

Why It Matters

Mozilla Firefox and its Extended Support Release channels carry a high-severity memory-corruption defect (CVSS 8.8) that can be reached through ordinary web browsing, with the potential for an attacker to escalate privileges on an affected endpoint. Because Firefox is broadly deployed across the workforce, unpatched browsers represent an exposure point for credential theft and endpoint compromise, and there is no public exploit identified at time of analysis, with exploitation rated as not automatable and the flaw requiring the user to load attacker-controlled content. Leadership should treat this as a bounded, scheduled remediation item rather than a crisis, while ensuring the organization does not drift into long-term exposure on outdated browsers.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.3%
Top 82% exploitable
Prevalence
Ubiquitous
Firefox is one of the most widely deployed browsers worldwide across all sectors
Data Quality
6 sources
Confidence: High

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 HIGH
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

44
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

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

Vendor StatusVendor

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