CVE-2022-40958Network attack vector

Session fixation via cookie prefix bypass

Published Dec 22, 2022 · Updated Apr 15, 2025

Improper input neutralization in Mozilla Firefox before 105 allows remote attackers on a shared insecure subdomain to overwrite secure cookies. The cookie parser accepts special-character forms that create nameless or misleading cookie pairs, bypassing __Host and __Secure prefix restrictions. Exploitation requires control of a sibling subdomain that is not a secure context and can lead to session fixation and related integrity attacks.

CVSS severity6.5
Medium
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input neutralization in Mozilla Firefox before 105 allows remote attackers on a shared insecure subdomain to overwrite secure cookies. The cookie parser accepts special-character forms that create nameless or misleading cookie pairs, bypassing __Host and __Secure prefix restrictions. Exploitation requires control of a sibling subdomain that is not a secure context and can lead to session fixation and related integrity attacks.

The record

CVE
CVE-2022-40958
Published
Dec 22, 2022
Updated
Apr 15, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-74, T1606.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 22, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record 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 <105

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <105
Mozilla · Thunderbirdversion=unspecified <102.3
Mozilla · Firefox ESRversion=unspecified <102.3

Published CVSS scores

6.5NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1606.001Forge Web Credentials: Web Cookies

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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