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Thunderbird CVE-2026-2767

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
    Deliver malicious WebAssembly module
  2. Exploit
    Browser parses and compiles WASM code
  3. Execution
    Use-after-free in JS engine memory
  4. Impact
    Execute arbitrary code with browser privileges

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A06:2021 - Vulnerable and Outdated Components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 default Firefox or Thunderbird installations via malicious WebAssembly content.
Impact

CVSS 9.8. WebAssembly UAFs can be triggered by sites using Wasm, which is increasingly common.
Exploit ScenarioDerived

Attacker serves WebAssembly module that triggers UAF in the Wasm runtime, achieving code execution.
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 JavaScript WebAssembly component before 148. WebAssembly-specific memory management bug.

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

UAF in Firefox WebAssembly component.

RemediationAI

Update Firefox 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 WebAssembly runtime. Memory management error specific to Wasm execution.

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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 - 08:30 nvd
Patch available
CVE Published
Feb 24, 2026 - 14:16 nvd
CRITICAL 9.8

DescriptionNVD

Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.

Executive ViewAI

Why It Matters

A critical use-after-free vulnerability in Firefox and Thunderbird (CVE-2026-2767, CVSS 9.8) allows remote attackers to execute arbitrary code with no user interaction required. Organizations using affected versions face immediate risk of compromise through malicious websites or emails, potentially leading to data breach, lateral movement, and system takeover.

Business Impact: Severe
Compensating Controls

Disable JavaScript in Thunderbird email client if business operations permit; restrict WebAssembly execution via browser policy (Group Policy/Mobile Device Management); deploy WAF rules to block known malicious JavaScript payloads; isolate vulnerable systems on restricted network segments; enforce sandboxing for browser processes; route web traffic through advanced threat prevention gateway; disable automatic JavaScript execution for untrusted content sources. These are temporary mitigations only—patch deployment is mandatory.

Threat Intelligence Overview

EPSS Score
0.0%
Top 86% 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:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

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The crypto.generateCRMFRequest function in Mozilla Firefox before 23.0, Firefox ESR 17.x before 17.0.8, Thunderbird befo
CVE-2013-0757 CRITICAL POC
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CVE-2014-1510 CRITICAL POC
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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
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Alpine Linux: mozjs fixed in 128.3.1-r0
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-2013-2566 MEDIUM POC
5.9 Mar 15

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Same weakness CWE-416 – Use After Free

View all
CVE-2019-0708 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2014-0322 HIGH POC
8.8
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
9.8
CVE-2013-2551 HIGH POC
8.8

Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
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CVE-2021-34523 CRITICAL POC
9.0
CVE-2013-2251 CRITICAL POC
9.8
CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
8.8
CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

SUSE

Severity: High
Product Status
Container suse/sl-micro/6.0/baremetal-os-container:2.1.3-6.61 Container suse/sl-micro/6.0/base-os-container:2.1.3-7.27 Container suse/sl-micro/6.0/kvm-os-container:2.1.3-6.52 Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.63 Container suse/sl-micro/6.0/toolbox:13.2-9.16 Image SL-Micro Affected
Image SL-Micro-BYOS-GCE Image SUSE-Multi-Linux-Manager-Proxy-BYOS-GCE Image SUSE-Multi-Linux-Manager-Server-BYOS-GCE Affected
Image SLES12-SP5-SAP-Azure-LI-BYOS-Production Image SLES12-SP5-SAP-Azure-VLI-BYOS-Production Affected
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-SP7-SAP-Azure-LI-BYOS-Production Image SLES15-SP7-SAP-Azure-VLI-BYOS-Production Affected
SUSE Liberty Linux 8 Fixed

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:3338 ADVISORY https://access.redhat.com/errata/RHSA-2026:3339 ADVISORY https://access.redhat.com/errata/RHSA-2026:3361 ADVISORY https://access.redhat.com/errata/RHSA-2026:3491 ADVISORY https://access.redhat.com/errata/RHSA-2026:3492 ADVISORY https://access.redhat.com/errata/RHSA-2026:3493 ADVISORY https://access.redhat.com/errata/RHSA-2026:3494 ADVISORY https://access.redhat.com/errata/RHSA-2026:3495 ADVISORY https://access.redhat.com/errata/RHSA-2026:3496 ADVISORY https://access.redhat.com/errata/RHSA-2026:3497 ADVISORY https://access.redhat.com/errata/RHSA-2026:3515 ADVISORY https://access.redhat.com/errata/RHSA-2026:3516 ADVISORY https://access.redhat.com/errata/RHSA-2026:3517 ADVISORY https://access.redhat.com/errata/RHSA-2026:3976 ADVISORY https://access.redhat.com/errata/RHSA-2026:3978 ADVISORY https://access.redhat.com/errata/RHSA-2026:3979 ADVISORY https://access.redhat.com/errata/RHSA-2026:3980 ADVISORY https://access.redhat.com/errata/RHSA-2026:3981 ADVISORY https://access.redhat.com/errata/RHSA-2026:3982 ADVISORY https://access.redhat.com/errata/RHSA-2026:3983 ADVISORY https://access.redhat.com/errata/RHSA-2026:3984 ADVISORY https://access.redhat.com/errata/RHSA-2026:4022 ADVISORY https://access.redhat.com/errata/RHSA-2026:4152 ADVISORY https://access.redhat.com/errata/RHSA-2026:4260 ADVISORY https://access.redhat.com/errata/RHSA-2026:4432 ADVISORY https://vuldb.com/vuln/347556 ADVISORY https://www.mozilla.org/security/advisories/mfsa2026-13/ ADVISORY https://www.mozilla.org/security/advisories/mfsa2026-15/ ADVISORY https://www.mozilla.org/security/advisories/mfsa2026-16/ ADVISORY https://www.mozilla.org/security/advisories/mfsa2026-17/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0812/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0871/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0880/ REF https://access.redhat.com/security/cve/CVE-2026-2767 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2013741 REF https://bugzilla.redhat.com/show_bug.cgi?id=2442328 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2767.json

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