CVE-2021-29963Network attack vector

Private-search correlation via shared normal-session cookies

Published Jun 24, 2021 · Updated Aug 3, 2024

Privacy exposure in Mozilla Firefox for Android before 89 allows attackers operating a search provider to correlate private and normal sessions. SearchSuggestionProvider sends private-mode address-bar suggestion requests with cookies from the normal browsing session instead of separating their state. Private-mode search suggestions are disabled by default, and exposure requires enabling them and typing in the address bar, which reveals search terms and permits cross-session linkage.

CVSS severity4.3
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privacy exposure in Mozilla Firefox for Android before 89 allows attackers operating a search provider to correlate private and normal sessions. SearchSuggestionProvider sends private-mode address-bar suggestion requests with cookies from the normal browsing session instead of separating their state. Private-mode search suggestions are disabled by default, and exposure requires enabling them and typing in the address bar, which reveals search terms and permits cross-session linkage.

The record

CVE
CVE-2021-29963
Published
Jun 24, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-345
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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 <89

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <89

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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.

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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-345Insufficient Verification of Data Authenticity

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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