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Mozilla Firefox CVE-2026-100801

| EUVDEUVD-2026-88954 HIGH
Improper Privilege Management (CWE-269)
2026-09-29 mozilla GHSA-7f52-cp5w-7wmh
High
Disputed · 8.8 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
    Firefox loads crafted content
  3. Exploit
    Trigger improper privilege management in DLL Services
  4. Execution
    Escalate privileges
  5. Impact
    Achieve high-impact code execution

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V8 - Authorization Least privilege enforcement
MITRE ATT&CK

1 technique across 1 tactic: 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 open attacker-controlled web content in Firefox (CVSS UI:R) - there is no unauthenticated drive-by against a service; a user must be induced to visit or render a crafted page. No authentication is required (PR:N) and complexity is low (AC:L). The affected code is the Windows-oriented 'DLL Services' component, so exposure is likely limited to Windows builds of Firefox; the flaw is fixed by updating to Firefox 157, ESR 153.4, or ESR 140.17, so unpatched pre-157/pre-ESR builds are the exposed population. Limiting factors: mandatory user interaction (not automatable per SSVC), no observed exploitation, and no public POC. Note the component/CWE vs AV:N tension above - if a local DLL search-path or side-loading precondition actually applies, real-world exploitability is narrower than the network vector suggests.

Impact

This is a genuine but not top-tier priority. The CVSS 3.1 base score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) reflects a network-reachable, low-complexity, unauthenticated flaw requiring only that a victim visit a malicious page, with total loss of confidentiality, integrity, and availability. CISA's SSVC decision framework agrees on impact (Technical Impact: total) but tempers urgency: Exploitation is 'none' (no observed exploitation) and Automatable is 'no' (the UI:R requirement prevents mass, wormable scanning-and-exploiting). There is no EPSS score, no CISA KEV listing, and no public POC - exploitation status is therefore 'no public exploit identified at time of analysis.' The signals are internally consistent (self-reported by Mozilla, patched proactively, no exploitation evidence), so this is a serious-severity-but-low-real-world-pressure issue typical of a vendor-disclosed browser bug. One genuine tension to verify: the CWE-269 classification plus the 'DLL Services' component name suggest a Windows DLL loading/privilege-management issue that would normally imply local prerequisites (AV:L), yet Mozilla's vector asserts AV:N with UI:R - verify with vendor whether remote web content alone triggers the escalation or whether local DLL search-path/side-loading conditions are also required.

Exploit ScenarioDerived

An attacker hosts or compromises a web page and lures a Firefox user into visiting it. On load, crafted content abuses the improper privilege management in the DLL Services component to escalate privileges within or beyond the browser process, yielding high-impact code execution. No public exploit code has been identified, and the required user interaction (visiting the page) means exploitation is not automatable at scale.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 29, 2026

Privilege escalation in the DLL Services component of Mozilla Firefox allows an attacker to achieve elevated code execution - with high confidentiality, integrity, and availability impact - when a victim renders attacker-controlled web content, reflected in a CVSS 3.1 score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H). No authentication is required (PR:N) and attack complexity is low, but the vector mandates user interaction (UI:R), meaning a target must be induced to load a crafted page rather than being compromised by a service-side drive-by. The issue is fixed in Firefox 157, Firefox ESR 153.4, and Firefox ESR 140.17, so unpatched pre-157 and pre-ESR builds are the exposed population; there is no public exploit code and no observed exploitation at time of analysis, and SSVC classifies the flaw as non-automatable.

RemediationAI

Apply the vendor-released fix by upgrading to Mozilla Firefox 157, Firefox ESR 153.4, or Firefox ESR 140.17 - Mozilla released these versions specifically to address this privilege-escalation issue, and the fixes are documented in advisories MFSA 2026-100, MFSA 2026-99, and MFSA 2026-97. Prioritize Windows endpoints, since the vulnerable DLL Services component is Windows-oriented and therefore the realistic exposure surface; inventory and force-update any remaining pre-157 and pre-ESR builds, including portable and user-installed copies that may sit outside managed patching. Because there is no vendor workaround that fully removes the flaw and no public exploit code has been identified, patching is the only complete fix; until updates can be deployed, reduce the attack surface by restricting browsing of untrusted or unsolicited web content to hardened or isolated environments, enforcing Windows DLL safe-search mode and signed-DLL-only loading policies so that dropped libraries cannot be loaded by firefox.exe, running the browser as an unprivileged user, and monitoring for unexpected module loads or privilege transitions in the Firefox process - each of these lowers but does not eliminate risk, and none should be treated as a substitute for the version upgrade. Verify remediation with the exact fixed build numbers on each channel and re-check the Mozilla advisories linked above for any revision.

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

The affected code is Firefox's 'DLL Services' component, a Windows-oriented subsystem that loads and manages dynamically linked libraries for browser features, and the assigned weakness is CWE-269 (Improper Privilege Management). That class of bug means the component does not correctly enforce the boundary between the privilege level of the content that triggered a DLL-related operation and the privilege level at which the resulting code actually runs, letting a lower-privileged context gain capabilities it should not have. The CPE entry cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* is an unversioned wildcard for the Mozilla Firefox product, so the advisory record itself does not narrow down affected builds beyond the fixed versions listed by the vendor. Because DLL loading on Windows is normally a local, filesystem-adjacent operation, the network-facing AV:N/UI:R vector is somewhat unusual for a DLL Services flaw: as recorded, the trigger is remote content delivered to the browser and the user interaction supplies the execution step, but the Windows-only nature of the component means the practical exposure is likely limited to Windows installations of Firefox rather than all platforms. If a local DLL search-path or side-loading precondition were in fact required, real-world exploitability would be narrower than the network vector implies; the independent assessment flags this component-versus-vector tension explicitly and does not treat the flaw as a remote unauthenticated drive-by. Relevant advisories are Mozilla MFSA 2026-97, MFSA 2026-99, and MFSA 2026-100, with the underlying report tracked in Mozilla Bugzilla 2057112 and mirrored as EUVD-2026-88954.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Sources disagree (Medium–Critical)
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

Deferring to Mozilla's browser-visit model (AV:N/UI:R, PR:N, S:U) with full C/I/A impact from privilege escalation; AV:L would be plausible if DLL-loading preconditions apply.

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
SUSE CRITICAL
Red Hat 6.1 MEDIUM

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

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

3
CVSS changed
Sep 29, 2026 - 14:22 NVD
8.8 (HIGH)
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 in the DLL Services component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

Executive ViewAI

Why It Matters

A high-severity privilege-escalation flaw in Mozilla Firefox's DLL Services component lets attacker-controlled web content escape the browser's normal security boundary and execute code with elevated privileges on the endpoint, affecting confidentiality, integrity, and availability alike. Any employee, contractor, or executive who browses the web with an unpatched Firefox build - standard, ESR, or 140.x ESR - is a potential victim and would need only to open a crafted page for a full endpoint compromise to follow. Because the flaw requires no credentials and only a single user interaction, it is a realistic phishing or malicious-advertising vector against a widely deployed desktop application, and leadership should treat timely browser patching as the primary risk-reduction lever.

Business Impact: High
Compensating Controls

Apply vendor patch (Firefox 157, Firefox ESR 153.4, Firefox ESR 140.17). Until patching completes: enforce auto-update and block vulnerable builds via application allow-listing where feasible, segment or restrict high-privilege work to hardened or alternative browsers, reduce exposure to untrusted web content through phishing-resistant email and web filtering, and monitor endpoint telemetry for unexpected privilege escalation or DLL loading activity originating from Firefox processes. Confirm actual patch availability and release artifacts with Mozilla before relying on version numbers cited in the assessment input.

Threat Intelligence Overview

EPSS Score
0.2%
Top 85% exploitable
Prevalence
Ubiquitous
Firefox is one of the most widely deployed browsers worldwide
Data Quality
5 sources
Confidence: Medium
EUVD NVD CVE.org EPSS Vulnrichment Vendor VulDB

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 0.2%
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.

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

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected
SUSE Linux Enterprise Module for Package Hub 15 SP7 Affected
SUSE Linux Enterprise Server 15 SP7 Affected

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