CVE-2021-29971Network attack vector

Permission inheritance via host-only origin comparison

Published Aug 5, 2021 · Updated Aug 3, 2024

Origin isolation failure in Mozilla Firefox for Android before 90 allows remote attackers to inherit saved site permissions. The Android Components site-permissions database stores only the host name, so permission lookup omits the scheme and port required to separate origins. Exploitation requires a previously saved grant and a page on the same host; inherited access is limited to that granted permission.

CVSS severityUnavailable
Unscored
EPSS probability1.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Origin isolation failure in Mozilla Firefox for Android before 90 allows remote attackers to inherit saved site permissions. The Android Components site-permissions database stores only the host name, so permission lookup omits the scheme and port required to separate origins. Exploitation requires a previously saved grant and a page on the same host; inherited access is limited to that granted permission.

The record

CVE
CVE-2021-29971
Published
Aug 5, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 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 <90

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <90

Published CVSS scores

No CVSS assessment is available in this record.

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

No sourced classifications are available.

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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