CVE-2026-2802Network attack vector

Data exposure and modification via GC race

Published Feb 24, 2026 · Updated Feb 24, 2026

A race condition in Mozilla Firefox and Thunderbird before 148 allows remote attackers to read or alter data via crafted web content. JavaScript GC gray-bit marking iterates symbol arenas while background sweeping can modify the same list, invalidating an element during traversal. Exploitation requires user interaction and favorable GC timing and thread scheduling; Thunderbird email reading disables scripting, limiting exposure to browser-like contexts.

CVSS severity4.2
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A race condition in Mozilla Firefox and Thunderbird before 148 allows remote attackers to read or alter data via crafted web content. JavaScript GC gray-bit marking iterates symbol arenas while background sweeping can modify the same list, invalidating an element during traversal. Exploitation requires user interaction and favorable GC timing and thread scheduling; Thunderbird email reading disables scripting, limiting exposure to browser-like contexts.

The record

CVE
CVE-2026-2802
Published
Feb 24, 2026
Updated
Feb 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-362, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <148

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <148
Mozilla · Thunderbirdversion=unspecified <148

Published CVSS scores

4.2CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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