Is CVE-2021-23969 in the CISA KEV catalog?

No. CVE-2021-23969 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-23969?

CVE-2021-23969 has a CVSS v3 base score of 4.3 (MEDIUM).

What is the EPSS score for CVE-2021-23969?

CVE-2021-23969 has an EPSS score of 1.21% (65th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-23969?

Upgrade firefox on debian unstable to 86.0-1 or later. Fixes are available for 7 affected products.

CVE & CISA-KEV Catalog

CVE-2021-23969

MEDIUM

4.3

CVSS v3

NVD

Description

As specified in the W3C Content Security Policy draft, when creating a violation report, "User agents need to ensure that the source file is the URL requested by the page, pre-redirects. If that’s not possible, user agents need to strip the URL down to an origin to avoid unintentional leakage." Under certain types of redirects, Firefox incorrectly set the source file to be the destination of the redirects. This was fixed to be the redirect destination's origin. This vulnerability affects Firefox < 86, Thunderbird < 78.8, and Firefox ESR < 78.8.

How to fix

Remediation Available

firefoxDebian

Fixed in:86.0-1CVE-2021-23969

firefoxUbuntu

Fixed in:86.0+build3-0ubuntu0.16.04.1USN-4756-1

Fixed in:86.0+build3-0ubuntu0.18.04.1USN-4756-1

Fixed in:86.0+build3-0ubuntu0.20.04.1USN-4756-1

thunderbirdUbuntu

Fixed in:1:78.8.1+build1-0ubuntu0.20.04.1USN-4936-1

DeveloperEditionWindows application

Affected:86.0Fixed in:86.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:86.0Fixed in:86.0Mozilla

Mozilla Firefox ESR (en-US)Windows application

Affected:78.8Fixed in:78.8Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:78.8Fixed in:78.8Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Exploit Intelligence

1.21%probability of exploitation in 30 days

65thpercentile

Moderate risk: more likely to be exploited than 65% of all known CVEs.

References

Vendor Advisory4

Third-Party Advisory4

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.