What’s Vulnerable › Vulnerabilities

CVE-2023-4583: Browsing Context potentially not cleared when closing Private Window

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-09-11 · updated 2026-06-17
• Weakness: CWE-754

Description

When checking if the Browsing Context had been discarded in `HttpBaseChannel`, if the load group was not available then it was assumed to have already been discarded which was not always the case for private channels after the private session had ended. This vulnerability affects Firefox < 117, Firefox ESR < 115.2, and Thunderbird < 115.2.

Affected products

• Mozilla Firefox: before 117.0 — fixed in 117.0
• Mozilla Firefox ESR: before 115.2 — fixed in 115.2
• Mozilla Thunderbird: before 115.2 — fixed in 115.2

How to fix

Upgrade to a fixed version: Mozilla Firefox 117.0; Mozilla Firefox ESR 115.2; Mozilla Thunderbird 115.2. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1842030
• https://www.mozilla.org/security/advisories/mfsa2023-34/
• https://www.mozilla.org/security/advisories/mfsa2023-36/
• https://www.mozilla.org/security/advisories/mfsa2023-38/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1842030
• https://www.mozilla.org/security/advisories/mfsa2023-34/
• https://www.mozilla.org/security/advisories/mfsa2023-36/
• https://www.mozilla.org/security/advisories/mfsa2023-38/

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