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Thunderbird CVE-2026-2807

CRITICAL
Out-of-bounds Write (CWE-787)
2026-02-24 security@mozilla.org
RCE Buffer Overflow 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
    Open malicious webpage in Firefox/Thunderbird
  2. Exploit
    Trigger memory corruption via crafted content
  3. Impact
    Execute arbitrary code with browser privileges

Vulnerability Assessment

Weakness
CWE
CWE-787
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, write limits
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 browser configurations. User must open attacker-controlled webpage.
Impact

CVSS 9.8. Standard Mozilla advisory language for potentially exploitable memory bugs.
Exploit ScenarioDerived

Memory corruption potentially exploitable for code execution.
Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Memory safety bugs in Firefox 147 and Thunderbird 147 with evidence of memory corruption. Mainline-only bugs not present in ESR branches.

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

Memory safety bugs in Firefox/Thunderbird 147 mainline.

RemediationAI

Update Firefox/Thunderbird to 148+.

Affects your stack

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

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Technical ContextAI · show details

CWE-787 memory corruption bugs in mainline only. Evidence of memory corruption and presumed exploitability.

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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 CRITICAL
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

Memory safety bugs present in Firefox 147 and Thunderbird 147. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 148 and Thunderbird < 148.

Executive ViewAI

Why It Matters

Critical memory corruption vulnerabilities in Firefox 147 and Thunderbird 147 (CVSS 9.8) could allow attackers to execute arbitrary code on affected systems. With no patch currently available, any user or employee running these versions is at immediate risk of compromise through malicious websites or specially crafted content. Organizations must act urgently to mitigate exposure or restrict usage of these applications.

Business Impact: Severe
Compensating Controls

Downgrade to Firefox 146 or Thunderbird 146 (prior stable versions); disable JavaScript execution if operationally feasible; restrict web browsing to whitelisted internal sites only; implement network segmentation to limit lateral movement from compromised endpoints; enforce browser security extensions with sandbox capabilities; disable email preview and automatic content loading in Thunderbird; monitor for suspicious process execution and memory access patterns; block external email attachments that may trigger exploitation vectors.

Threat Intelligence Overview

EPSS Score
0.1%
Top 83% 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 0.1%
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

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.

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.

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)NVD

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

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Same weakness CWE-787 – Out-of-bounds Write

View all
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CVE-2014-1761 HIGH POC
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Same technique RCE

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Vendor StatusVendor

SUSE

Severity: Critical
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/347570 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-2026-2807 REF https://bugzilla.mozilla.org/buglist.cgi?bug_id=1756056%2C1999402%2C2004872%2C2006037%2C2012855 REF https://bugzilla.redhat.com/show_bug.cgi?id=2442296 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2807.json

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