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FirefoxWeb browser · Mozilla

CVE-2024-7527

HIGH · 8.8 CVSS v3.1 Published 2024-08-06
Fix available
A fix is available. Upgrade to 115.14.0 / 129.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Unexpected marking work at the start of sweeping could have led to a use-after-free. This vulnerability affects Firefox < 129, Firefox ESR < 115.14, Firefox ESR < 128.1, Thunderbird < 128.1, and Thunderbird < 115.14.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A use-after-free vulnerability exists in Firefox and Thunderbird's garbage collection implementation. The issue occurs when unexpected marking work takes place at the start of the sweeping phase, causing memory to be accessed after it has been freed. This is a memory safety flaw in the SpiderMonkey JavaScript engine's GC subsystem.

MitigationUpdate affected installations to Firefox 129, Firefox ESR 115.14/128.1, or Thunderbird 115.14/128.1 or later to receive the vendor patch. No workarounds are available for this memory corruption issue.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FirefoxWeb browser
Affected:< 129.0
Firefox EsrWeb browser
Affected:< 115.14.0= 128.0
ThunderbirdApplication
Affected:< 115.14.0= 128.0.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Mozilla product
    Check for Firefox or Thunderbird installation - on Windows check Program Files or registry, on Linux run 'which firefox' or 'which thunderbird', on Mac check /Applications folder for Firefox.app or Thunderbird.app
    Affected if Neither Firefox nor Thunderbird is installed (not affected)
  2. Determine Firefox version
    Run 'firefox --version' or access about:Firefox page in browser address bar to retrieve version number
    Affected if Firefox version is less than 129.0, or is ESR 115.x below 115.14.0, or is exactly 128.0 (any channel)
  3. Determine Thunderbird version
    Run 'thunderbird --version' or access about:Thunderbird page to retrieve version number
    Affected if Thunderbird version is less than 115.14.0, or is exactly 128.0.1
  4. Confirm garbage collection is active
    This vulnerability affects the garbage collection sweeping phase - the feature is always active during normal browser/mail operation; no special config check needed - the flaw exists in the core GC mechanism itself
    Affected if Any version matching the affected ranges above is in use

You are affected if Firefox version is below 129.0 (including any ESR 115.x below 115.14.0 or exactly 128.0) or Thunderbird version is below 115.14.0 or exactly 128.0.1.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 115.14.0 / 129.0 or later
Fixed in 115.14.0129.0
Interim mitigation

Update affected installations to Firefox 129, Firefox ESR 115.14/128.1, or Thunderbird 115.14/128.1 or later to receive the vendor patch. No workarounds are available for this memory corruption issue.

Recommended fix High confidence

Firefox 129.0; Firefox ESR 128.1 or 115.14.0; Thunderbird 128.1 or 115.14.0

  1. Upgrade Firefox to version 129.0 or later
  2. If using Firefox ESR 115.x branch, upgrade to version 115.14.0 or later
  3. If using Firefox ESR 128.x branch, upgrade to version 128.1 or later
  4. If using Thunderbird 115.x branch, upgrade to version 115.14.0 or later
  5. If using Thunderbird 128.x branch, upgrade to version 128.1 or later
  6. Restart the application after upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA3.0 h
17.0 hours of engineering $2,860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,576.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-7527 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data