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Firefox Esr EUVDEUVD-2026-14802

| CVE-2026-4689 CRITICAL
Classic Buffer Overflow (CWE-120)
2026-03-24 mozilla
Buffer Overflow Mozilla Firefox Esr
10.0
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Deliver malicious webpage with crafted content
  2. Exploit
    Trigger integer overflow in XPCOM component
  3. Execution
    Escape sandbox restrictions
  4. Impact
    Execute arbitrary code with system privileges

Vulnerability Assessment

Weakness
CWE
CWE-120
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Buffer copy size validation
MITRE ATT&CK

1 technique across 1 tactic: Execution

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

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Exploitation Conditions

Remote unauthenticated attacker exploiting Firefox < 149, Firefox ESR < 115.34, or Firefox ESR < 140.9 through malicious web content. No user interaction required beyond visiting a crafted webpage. XPCOM sandbox escape via integer overflow in boundary condition handling.
Impact

This vulnerability presents significant real-world risk despite missing CVSS and EPSS scores in the provided data. The attack vector is network-based (web content can trigger the flaw), and while the complexity is moderate to high (requires precise exploitation of integer overflow conditions), a successful exploit results in complete sandbox bypass—a critical technical impact. The Mozilla advisory references (MFSA2026-20, MFSA2026-21, MFSA2026-22) suggest this was actively being tracked and remedied across multiple Firefox release channels, indicating Mozilla treated this as high priority. The sandbox escape capability elevates this beyond typical memory corruption bugs; attackers gaining code execution outside the sandbox can compromise the entire system. The existence of multiple CVE advisories and the specific version thresholds (Firefox < 149, ESR < 115.34, < 140.9) indicate coordinated patching efforts. Without public POC or KEV data in the provided intelligence, exploitation likelihood depends on the sophistication of the integer overflow trigger, but sandbox escapes are historically high-value targets for advanced threat actors.
Exploit ScenarioDerived

An attacker crafts a malicious webpage containing specially crafted JavaScript that triggers the integer overflow condition in XPCOM's boundary handling code. When a user visits the page, the overflow causes memory corruption that allows the attacker to escape the Firefox sandbox, granting code execution outside the browser's security boundary. From this position, the attacker can access the user's file system, steal credentials, install malware, or escalate privileges on the host system. The network attack vector and moderate complexity suggest this requires technical sophistication, but the high impact of sandbox escape makes it an attractive target for nation-state and advanced cybercriminal actors.
Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

A sandbox escape vulnerability exists in Firefox's XPCOM component due to incorrect boundary conditions and integer overflow, allowing attackers to bypass security sandboxing mechanisms. This affects Firefox versions below 149, Firefox ESR below 115.34, and Firefox ESR below 140.9. An attacker can exploit this flaw to escape the browser sandbox and potentially execute arbitrary code with elevated privileges on the affected system.

RemediationAI

Immediately upgrade Firefox to version 149 or later, or upgrade Firefox ESR to version 115.34 or later if using the 115.x branch, or version 140.9 or later if using the 140.x branch. Detailed patching guidance is available in the Mozilla security advisories at https://www.mozilla.org/security/advisories/mfsa2026-20/, https://www.mozilla.org/security/advisories/mfsa2026-21/, and https://www.mozilla.org/security/advisories/mfsa2026-22/. As a temporary mitigation pending patching, disable or restrict JavaScript execution in untrusted content and limit browsing to known trusted websites, though these measures provide only partial protection given the sandbox escape nature of the vulnerability. Organizations should prioritize patching within 24-48 hours given the critical nature of sandbox bypass flaws.

Affected VersionsENISA

Firefox ESR unspecified <115.34
Firefox ESR unspecified <140.9
Firefox unspecified <149

Affected Packages

euvd firefox_esr_unspecified fix: 115.34, 140.9
euvd firefox_unspecified fix: 149

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

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Technical ContextAI · show details

The vulnerability resides in Mozilla Firefox's XPCOM (Cross Platform Component Object Model) component, which is Mozilla's framework for creating reusable software components. The root cause involves incorrect boundary condition checks combined with integer overflow, classified under buffer overflow vulnerabilities (CWE category). XPCOM is a core architectural component responsible for managing inter-process communication and memory allocation within Firefox. The integer overflow condition likely allows an attacker to manipulate memory boundaries, bypassing the sandbox's isolation mechanisms that normally restrict web content from accessing system resources. The affected products are identified via CPE strings: cpe:2.3:a:mozilla:firefox (all versions), cpe:2.3:a:mozilla:firefox_esr (both ESR branches), indicating both the rapid-release and extended support release channels are impacted.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 10.0 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
SUSE 8.3 HIGH
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Red Hat 7.5 HIGH

Primary rating from NVD.

CVSS VectorNVD

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

Lifecycle Timeline

3
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
PoC Detected
Mar 25, 2026 - 15:34 vuln.today
Public exploit code
CVE Published
Mar 24, 2026 - 12:30 nvd
CRITICAL 10.0

DescriptionNVD

Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

Organizations using the XPCOM component. This vulnerability affects Firefox face critical risk from CVE-2026-4689, a buffer overflow vulnerability rated CVSS 10.0. Exploitation could allow attackers to corrupt memory, crash the application, or potentially execute arbitrary code. Organizations should apply vendor updates immediately when available and implement compensating controls in the interim.

Business Impact: Severe
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

EPSS Score
0.0%
Top 99% exploitable
Exploit
POC
Public exploit code exists
Data Quality
8 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor GitHub 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 CRITICAL
CISA KEV No
Public POC Yes
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity + public POC available
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
Very High
Technical Impact
Total

Priority Score

70
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +50
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

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.

More in Firefox Esr

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3.7 May 21

The TLS protocol 1.2 and earlier, when a DHE_EXPORT ciphersuite is enabled on a server but not on a client, does not pro
CVE-2020-26950 HIGH POC
8.8 Dec 09

In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable

CVE-2022-29917 CRITICAL POC
9.8 Dec 22

Mozilla developers Andrew McCreight, Gabriele Svelto, Tom Ritter and the Mozilla Fuzzing Team reported memory safety bug
CVE-2014-1568 HIGH
7.5 Sep 25

Mozilla Network Security Services (NSS) before 3.16.2.1, 3.16.x before 3.16.5, and 3.17.x before 3.17.1, as used in Mozi
CVE-2022-26384 CRITICAL POC
9.6 Dec 22

If an attacker could control the contents of an iframe sandboxed with <code>allow-popups</code> but not <code>allow-scri
CVE-2022-34484 HIGH POC
8.8 Dec 22

The Mozilla Fuzzing Team reported potential vulnerabilities present in Thunderbird 91.10. Rated high severity (CVSS 8.8)
CVE-2022-28281 HIGH POC
8.8 Dec 22

If a compromised content process sent an unexpected number of WebAuthN Extensions in a Register command to the parent pr
CVE-2022-26381 HIGH POC
8.8 Dec 22

An attacker could have caused a use-after-free by forcing a text reflow in an SVG object leading to a potentially exploi
CVE-2022-22756 HIGH POC
8.8 Dec 22

If a user was convinced to drag and drop an image to their desktop or other folder, the resulting object could have been
CVE-2022-22740 HIGH POC
8.8 Dec 22

Certain network request objects were freed too early when releasing a network request handle. Rated high severity (CVSS

CVE-2022-22738 HIGH POC
8.8 Dec 22

Applying a CSS filter effect could have accessed out of bounds memory. Rated high severity (CVSS 8.8), this vulnerabilit
CVE-2021-29988 HIGH POC
8.8 Aug 17

Firefox incorrectly treated an inline list-item element as a block element, resulting in an out of bounds read or memory

Same weakness CWE-120 – Classic Buffer Overflow

View all
CVE-2017-7269 CRITICAL POC
9.8
CVE-2019-11043 CRITICAL POC
9.8
CVE-2016-10174 CRITICAL POC
9.8
CVE-2016-0099 HIGH POC
7.8
CVE-2016-6366 HIGH POC
8.8
CVE-2013-1331 HIGH
7.8
CVE-2013-0641 HIGH
7.8
CVE-2017-15222 CRITICAL POC
9.8

Same technique Buffer Overflow

View all
CVE-2015-5119 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
9.8
CVE-2011-2462 CRITICAL POC
9.8
CVE-2020-0796 CRITICAL POC
10.0
CVE-2009-0927 HIGH POC
8.8
CVE-2012-1889 HIGH POC
8.8

Vendor StatusVendor

Debian

firefox
Release Status Fixed Version Urgency
sid vulnerable 148.0.2-1 -
(unstable) fixed (unfixed) -
firefox-esr
Release Status Fixed Version Urgency
bullseye vulnerable 115.14.0esr-1~deb11u1 -
bullseye (security) vulnerable 140.8.0esr-1~deb11u1 -
bookworm vulnerable 128.14.0esr-1~deb12u1 -
bookworm (security) vulnerable 140.8.0esr-1~deb12u1 -
trixie (security), trixie vulnerable 140.8.0esr-1~deb13u1 -
forky, sid vulnerable 140.8.0esr-1 -
(unstable) fixed (unfixed) -

SUSE

Severity: High
Product Status
Image SLES15-SP5-SAP-Azure-LI-BYOS Image SLES15-SP5-SAP-Azure-LI-BYOS-Production Image SLES15-SP5-SAP-Azure-VLI-BYOS Image SLES15-SP5-SAP-Azure-VLI-BYOS-Production Image SLES15-SP6-SAP-Azure-LI-BYOS Image SLES15-SP6-SAP-Azure-LI-BYOS-Production Image SLES15-SP6-SAP-Azure-VLI-BYOS Image SLES15-SP6-SAP-Azure-VLI-BYOS-Production Image SLES15-SP7-SAP-Azure-LI-BYOS-Production Image SLES15-SP7-SAP-Azure-VLI-BYOS-Production Affected
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:5930 ADVISORY https://access.redhat.com/errata/RHSA-2026:5931 ADVISORY https://access.redhat.com/errata/RHSA-2026:5932 ADVISORY https://access.redhat.com/errata/RHSA-2026:6188 ADVISORY https://access.redhat.com/errata/RHSA-2026:6342 ADVISORY https://access.redhat.com/errata/RHSA-2026:6917 ADVISORY https://access.redhat.com/errata/RHSA-2026:7837 ADVISORY https://access.redhat.com/errata/RHSA-2026:7838 ADVISORY https://access.redhat.com/errata/RHSA-2026:7839 ADVISORY https://access.redhat.com/errata/RHSA-2026:7840 ADVISORY https://access.redhat.com/errata/RHSA-2026:7841 ADVISORY https://access.redhat.com/errata/RHSA-2026:7842 ADVISORY https://access.redhat.com/errata/RHSA-2026:7843 ADVISORY https://access.redhat.com/errata/RHSA-2026:7845 ADVISORY https://access.redhat.com/errata/RHSA-2026:7858 ADVISORY https://access.redhat.com/errata/RHSA-2026:8284 ADVISORY https://access.redhat.com/errata/RHSA-2026:8285 ADVISORY https://access.redhat.com/errata/RHSA-2026:8286 ADVISORY https://access.redhat.com/errata/RHSA-2026:8287 ADVISORY https://access.redhat.com/errata/RHSA-2026:8288 ADVISORY https://access.redhat.com/errata/RHSA-2026:8289 ADVISORY https://access.redhat.com/errata/RHSA-2026:8290 ADVISORY https://access.redhat.com/errata/RHSA-2026:8315 ADVISORY https://access.redhat.com/errata/RHSA-2026:8427 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-4689 ADVISORY https://vuldb.com/?id.352736 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1126/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1127/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1163/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20978/ REF https://access.redhat.com/errata/RHSA-2026:8850 REF https://access.redhat.com/security/cve/CVE-2026-4689 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2016374 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450718 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4689.json REF https://www.mozilla.org/security/advisories/mfsa2026-20/ REF https://www.mozilla.org/security/advisories/mfsa2026-21/ REF https://www.mozilla.org/security/advisories/mfsa2026-22/ REF https://www.mozilla.org/security/advisories/mfsa2026-23/ REF https://www.mozilla.org/security/advisories/mfsa2026-24/

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