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Thunderbird CVE-2026-2799

CRITICAL
Use After Free (CWE-416)
2026-02-24 security@mozilla.org
Information Disclosure Use After Free Memory Corruption Mozilla Thunderbird
9.8
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Send malicious HTML document
  2. Exploit
    Trigger DOM element reference after deallocation
  3. Impact
    Execute arbitrary code in browser process

Vulnerability Assessment

Weakness
CWE
CWE-416
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
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.

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Exploitation Conditions

No special conditions — remote unauthenticated exploitation against Firefox < 148 or Thunderbird < 148 with default configurations via malicious webpage.
Impact

CVSS 9.8.
Exploit ScenarioDerived

DOM manipulation triggers UAF.
Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Use-after-free in Firefox DOM Core & HTML before 148. DOM object lifecycle error.

Earlier versions of this analysis (1)
v1 Mar 12, 2026 - 21:55 CVSS 9.8

UAF in Firefox DOM Core.

RemediationAI

Update Firefox/Thunderbird to 148+.

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.

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Technical ContextAI · show details

CWE-416 UAF in DOM Core & HTML processing.

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

NVD PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SUSE 8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/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
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Patch released
Apr 10, 2026 - 14:30 nvd
Patch available
CVE Published
Feb 24, 2026 - 14:16 nvd
CRITICAL 9.8

DescriptionNVD

Use-after-free in the DOM: Core & HTML component. This vulnerability affects Firefox < 148 and Thunderbird < 148.

Executive ViewAI

Why It Matters

A critical use-after-free vulnerability in Firefox and Thunderbird (versions below 148) poses immediate risk to organizations relying on these applications for business communication and web access. With a CVSS score of 9.8 and no patch currently available, attackers could exploit this to achieve remote code execution on affected systems, potentially compromising sensitive data and business operations.

Business Impact: Severe
Compensating Controls

Implement application whitelisting to restrict Firefox/Thunderbird execution; deploy endpoint detection and response (EDR) with use-after-free exploit signature detection; enforce network segmentation to limit lateral movement if compromise occurs; disable JavaScript execution in Thunderbird; implement browser isolation technology for high-risk users; configure web content filtering to block known malicious domains; increase email security scanning and sandboxing; disable DOM-heavy web features if technically feasible.

Threat Intelligence Overview

EPSS Score
0.0%
Top 87% exploitable
Data Quality
5 sources
Confidence: Medium
NVD CVE.org EPSS 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 CRITICAL
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
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
Out-of-Cycle
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
Very High

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Use After Free HIGH

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

Memory Corruption HIGH

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 MEDIUM

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

Affected Products (CPE)NVD

cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

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Same weakness CWE-416 – Use After Free

View all
CVE-2019-0708 CRITICAL POC
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CVE-2015-5119 CRITICAL POC
9.8
CVE-2014-0322 HIGH POC
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CVE-2012-4792 HIGH POC
8.8
CVE-2009-4324 HIGH POC
7.8
CVE-2015-0313 CRITICAL POC
9.8
CVE-2015-5122 CRITICAL POC
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CVE-2013-2551 HIGH POC
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Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
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CVE-2021-34523 CRITICAL POC
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CVE-2013-2251 CRITICAL POC
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CVE-2017-5638 CRITICAL POC
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CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
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CVE-2015-1701 HIGH POC
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CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

SUSE

Severity: High
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Fixed

References

Advisories & patches
ADVISORY https://vuldb.com/vuln/347582 ADVISORY https://www.mozilla.org/security/advisories/mfsa2026-13/ ADVISORY https://www.mozilla.org/security/advisories/mfsa2026-16/ REF https://access.redhat.com/security/cve/CVE-2026-2799 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2014551 REF https://bugzilla.redhat.com/show_bug.cgi?id=2442303 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2799.json

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