CVE-2020-26975Public exploit

Session fixation via unrestricted Intent header injection

Published Jan 7, 2021 · Updated Aug 4, 2024

Header injection in Mozilla Firefox for Android before 84 allows local users to fix web sessions through a malicious application's crafted Intent. CustomTabIntentProcessor accepts the Browser.EXTRA_HEADERS Bundle without filtering forbidden names, allowing Cookie and Sec-* headers into Firefox requests. Exploitation requires a malicious application installed on the device; injected cookies can bind the browser to an attacker-known session.

CVSS severity6.5
Medium
EPSS probability0.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Header injection in Mozilla Firefox for Android before 84 allows local users to fix web sessions through a malicious application's crafted Intent. CustomTabIntentProcessor accepts the Browser.EXTRA_HEADERS Bundle without filtering forbidden names, allowing Cookie and Sec-* headers into Firefox requests. Exploitation requires a malicious application installed on the device; injected cookies can bind the browser to an attacker-known session.

The record

CVE
CVE-2020-26975
Published
Jan 7, 2021
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
T1550.004
Attack vector
local
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 vectorlocal
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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1550.004Use Alternate Authentication Material: Web Session Cookie

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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