CVE-2020-26977Public exploitNetwork attack vector

URL spoofing via premature new-tab URL trust

Published Jan 7, 2021 · Updated Aug 4, 2024

URL spoofing in Mozilla Firefox for Android before 84 allows remote attackers to misrepresent a tab's origin through an unresponsive port. WindowFeature immediately stores a new window's requested URL as tab state, while Gecko's initial about:blank location update is suppressed, so injected content retains the requested domain in the address bar until the connection times out. A user must open the attacker-controlled page and trigger the new tab; the resulting mismatch can support phishing but does not affect desktop Firefox.

CVSS severity6.5
Medium
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

URL spoofing in Mozilla Firefox for Android before 84 allows remote attackers to misrepresent a tab's origin through an unresponsive port. WindowFeature immediately stores a new window's requested URL as tab state, while Gecko's initial about:blank location update is suppressed, so injected content retains the requested domain in the address bar until the connection times out. A user must open the attacker-controlled page and trigger the new tab; the resulting mismatch can support phishing but does not affect desktop Firefox.

The record

CVE
CVE-2020-26977
Published
Jan 7, 2021
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
T1456
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 <84

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <84

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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.

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 exploitPublished

Weakness, pattern, technique

T1456Drive-By Compromise

Public exploit references

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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