CVE-2021-29973Network attack vector

Password disclosure via interaction-free HTTP autofill

Published Aug 5, 2021 · Updated Aug 3, 2024

Password autofill in Mozilla Firefox for Android before 90 allows man-in-the-middle attackers to read saved credentials via altered HTTP pages. The mobile configuration set signon.autofillForms.http to true by default, causing password fields to autofill without explicit page interaction. Exploitation requires a user to visit an insecure HTTP origin with matching saved credentials; desktop platforms are unaffected.

CVSS severity8.8
High
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Password autofill in Mozilla Firefox for Android before 90 allows man-in-the-middle attackers to read saved credentials via altered HTTP pages. The mobile configuration set signon.autofillForms.http to true by default, causing password fields to autofill without explicit page interaction. Exploitation requires a user to visit an insecure HTTP origin with matching saved credentials; desktop platforms are unaffected.

The record

CVE
CVE-2021-29973
Published
Aug 5, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
T1056.003
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

8.8UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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

T1056.003Web Portal Capture

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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