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FirefoxWeb browser · Mozilla

CVE-2024-7531

MEDIUM · 6.5 CVSS v3.1 Published 2024-08-06
Fix available
A fix is available. Upgrade to 115.14.0 / 129.0 or later.
See remediation →
72/100
Remediation priority · Elevated
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
Calling `PK11_Encrypt()` in NSS using CKM_CHACHA20 and the same buffer for input and output can result in plaintext on an Intel Sandy Bridge processor. In Firefox this only affects the QUIC header protection feature when the connection is using the ChaCha20-Poly1305 cipher suite. The most likely outcome is connection failure, but if the connection persists despite the high packet loss it could be possible for a network observer to identify packets as coming from the same source despite a network path change. This vulnerability affects Firefox < 129, Firefox ESR < 115.14, and Firefox ESR < 128.1.

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

A vulnerability in NSS library's PK11_Encrypt() function when using CKM_CHACHA20 cipher allows plaintext to leak when the same buffer is used for input and output on Intel Sandy Bridge processors. In Firefox, this specifically impacts QUIC header protection when using ChaCha20-Poly1305 cipher suites, potentially allowing a network observer to correlate packets to the same source despite network path changes.

MitigationUpdate Firefox to version 129 or later, or to Firefox ESR 115.14+/128.1+ to remediate the vulnerability. For enterprises, deploy the update via standard software distribution mechanisms.

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

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
None
Availability
None

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

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. Check Firefox version
    Navigate to 'about:support' in the Firefox address bar or run 'firefox --version' from command line. The version is displayed at the top of the page or in the command output.
    Affected if The installed version is below 129.0, or is between 115.0 and 115.13.x, or is exactly 128.0.
  2. Verify processor is Intel Sandy Bridge
    On Windows, open Task Manager > Performance tab and look at the CPU name (e.g., Intel Core i7-2600). On Linux, run 'lscpu | grep -i model' or 'cat /proc/cpuinfo' and look for Sandy Bridge in the model name (family 6, model 0x2A or 0x2D).
    Affected if The processor is an Intel Sandy Bridge CPU (second generation Core i-series, typically model numbers 2xxx).
  3. Check QUIC protocol support
    In Firefox, navigate to 'about:config' and search for 'network.http.http3.enabled'. Also check for 'security.tls.enable.chacha20poly1305' to verify ChaCha20-Poly1305 support.
    Affected if HTTP/3 (QUIC) is enabled and ChaCha20 cipher suites are available in the browser.

A user is affected if they run an unpatched Firefox version (below 129.0 or ESR below 115.14.0/128.1) on Intel Sandy Bridge hardware while using QUIC with ChaCha20-Poly1305 cipher suites, allowing potential packet correlation by network observers.

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 Firefox to version 129 or later, or to Firefox ESR 115.14+/128.1+ to remediate the vulnerability. For enterprises, deploy the update via standard software distribution mechanisms.

Recommended fix High confidence

Firefox 129.0+ | Firefox ESR 115.14.0+ | Firefox ESR 128.1.0+

  1. Upgrade Firefox to version 129.0 or later
  2. If using Firefox ESR, upgrade to version 115.14.0 or later, or upgrade to version 128.1.0 or later
  3. After upgrading, verify the Firefox version by navigating to about:support or checking Help > About Firefox

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
Get the upgrade done

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-2024-7531 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