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FirefoxWeb browser · Mozilla

CVE-2025-2857

CRITICAL · 10.0 CVSS v3.1 Published 2025-03-27
Fix available
A fix is available. Upgrade to 115.21.1 / 128.8.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
Following the recent Chrome sandbox escape (CVE-2025-2783), various Firefox developers identified a similar pattern in our IPC code. A compromised child process could cause the parent process to return an unintentionally powerful handle, leading to a sandbox escape. The original vulnerability was being exploited in the wild. *This only affects Firefox on Windows. Other operating systems are unaffected.*. This vulnerability was fixed in Firefox 136.0.4, Firefox ESR 128.8.1, and Firefox ESR 115.21.1.

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 · high confidence

Windows-specific sandbox escape in Firefox IPC mechanism. A compromised child process can cause the parent process to return an unintentionally powerful handle, bypassing the sandbox. This is similar to Chrome CVE-2025-2783 and was being actively exploited in the wild.

MitigationImmediately upgrade Firefox to version 136.0.4, ESR 128.8.1, or ESR 115.21.1. This is a critical severity vulnerability being exploited in the wild; prioritize Windows deployments.

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:< 136.0.4< 115.21.1>= 128.1.0, < 128.8.1

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
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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. Confirm operating system is Windows
    Run 'systeminfo' or check System Properties to verify the OS. This vulnerability only affects Windows systems.
    Affected if The system is NOT running Windows (Linux/macOS are not affected by this specific flaw).
  2. Identify Firefox installation path and version
    Open Firefox, go to Help > About Firefox, or navigate to the Firefox program directory and check the version.ini file. Alternatively, run 'firefox --version' from command line if available.
    Affected if The installed Firefox version falls within these vulnerable ranges: < 136.0.4, < 115.21.1, or >= 128.1.0 but < 128.8.1.
  3. Check if Firefox is a Windows build
    In Firefox about:support page, look at the 'Build' information or check the executable properties - the vulnerable binary is the Windows-specific IPC implementation.
    Affected if The Firefox build is not the Windows version (non-Windows builds are not affected).

You are affected if running a vulnerable Firefox version (as listed above) on Windows, where a compromised child process could exploit the IPC mechanism to escape the sandbox.

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 115.21.1 / 128.8.1 / 136.0.4 or later
Fixed in 115.21.1128.8.1136.0.4
Interim mitigation

Immediately upgrade Firefox to version 136.0.4, ESR 128.8.1, or ESR 115.21.1. This is a critical severity vulnerability being exploited in the wild; prioritize Windows deployments.

Recommended fix High confidence

Firefox 136.0.4 (regular) / Firefox ESR 115.21.1 / Firefox ESR 128.8.1

  1. 1. Check current Firefox version by navigating to about:support or about:firefox in the address bar
  2. 2. Identify the installed Firefox edition and version (regular, ESR 115.x, or ESR 128.x)
  3. 3. Download Firefox 136.0.4 (or latest 136.x) from the official Mozilla website if using regular Firefox
  4. 4. Download Firefox ESR 115.21.1 (or latest 115.x) from the official Mozilla website if using Firefox ESR 115.x
  5. 5. Download Firefox ESR 128.8.1 (or latest 128.x) from the official Mozilla website if using Firefox ESR 128.x
  6. 6. Run the installer and restart Firefox after installation completes
  7. 7. Verify the upgrade by checking about:support to confirm the new version is installed
  8. 8. Note: This vulnerability only affects Firefox on Windows; Linux and macOS are unaffected

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
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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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-2025-2857 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