CVE-2024-7531Network attack vector

Connection linkability via failed QUIC header encryption

Published Aug 6, 2024 · Updated Mar 19, 2025

Information disclosure in Mozilla Firefox before 129 and Firefox ESR before 115.14 or 128.1 allows attackers to link QUIC packets. NSS ChaCha20Xor runs vectorized and scalar encryption over the same aliased input/output buffer, so the scalar pass decrypts the header-protection mask back to plaintext. Exposure requires an Intel Sandy Bridge processor, QUIC with ChaCha20-Poly1305, and a connection that persists through packet loss; the usual result is connection failure.

CVSS severity6.5
Medium
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Mozilla Firefox before 129 and Firefox ESR before 115.14 or 128.1 allows attackers to link QUIC packets. NSS ChaCha20Xor runs vectorized and scalar encryption over the same aliased input/output buffer, so the scalar pass decrypts the header-protection mask back to plaintext. Exposure requires an Intel Sandy Bridge processor, QUIC with ChaCha20-Poly1305, and a connection that persists through packet loss; the usual result is connection failure.

The record

CVE
CVE-2024-7531
Published
Aug 6, 2024
Updated
Mar 19, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-367, T1040
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 6, 2024CVE publishedPublication date reported by the CVE source.
  2. Mar 19, 2025Record 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 <129

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <129
Mozilla · Firefox ESRversion=unspecified <115.14; version=unspecified <128.1

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
6.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1040Network Sniffing

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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