CVE-2023-4583Network attack vector

Cross-session cookie leakage via stale private context

Published Sep 11, 2023 · Updated Dec 18, 2025

Improper state handling in Firefox before 117 and Firefox ESR and Thunderbird before 115.2 allows attackers to leak private-session cookies. HttpBaseChannel::IsBrowsingContextDiscarded uses missing load-group state instead of the global private-browsing state, so a late private-channel response can set cookies after the session ends. Triggering the leak requires a private response to complete after the last private window closes; the retained cookie can then authenticate a new private session.

CVSS severity7.5
High
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper state handling in Firefox before 117 and Firefox ESR and Thunderbird before 115.2 allows attackers to leak private-session cookies. HttpBaseChannel::IsBrowsingContextDiscarded uses missing load-group state instead of the global private-browsing state, so a late private-channel response can set cookies after the session ends. Triggering the leak requires a private response to complete after the last private window closes; the retained cookie can then authenticate a new private session.

The record

CVE
CVE-2023-4583
Published
Sep 11, 2023
Updated
Dec 18, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-754
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 18, 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 <117

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <117
Mozilla · Thunderbirdversion=unspecified <115.2
Mozilla · Firefox ESRversion=unspecified <115.2

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions

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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