CVE-2021-38492
CVE-2021-38492 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.
Key facts
- Severity: Medium (CVSS 3.x base score 6.5)
- CVSS v2: 4.3
- EPSS exploit prediction: 1% (62nd percentile)
- Actively exploited: Not listed in CISA KEV
- Affected product: Mozilla Firefox
- Published:
- Last modified:
Description
When delegating navigations to the operating system, Firefox would accept the `mk` scheme which might allow attackers to launch pages and execute scripts in Internet Explorer in unprivileged mode. *This bug only affects Firefox for Windows. Other operating systems are unaffected.*. This vulnerability affects Firefox < 92, Thunderbird < 91.1, Thunderbird < 78.14, Firefox ESR < 78.14, and Firefox ESR < 91.1.
Frequently asked questions
- What is CVE-2021-38492?
- When delegating navigations to the operating system, Firefox would accept the `mk` scheme which might allow attackers to launch pages and execute scripts in Internet Explorer in unprivileged mode. *This bug only affects Firefox for Windows. Other operating systems are unaffected.*. This vulnerability affects Firefox < 92, Thunderbird < 91.1, Thunderbird < 78.14, Firefox ESR < 78.14, and Firefox ESR < 91.1.
- How severe is CVE-2021-38492?
- CVE-2021-38492 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.
- Is CVE-2021-38492 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2021-38492?
- CVE-2021-38492 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2021-38492?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- When was CVE-2021-38492 published?
- CVE-2021-38492 was published on 2021-11-03 and last updated on 2026-06-17.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1721107
- https://security.gentoo.org/glsa/202208-14
- https://www.mozilla.org/security/advisories/mfsa2021-38/
- https://www.mozilla.org/security/advisories/mfsa2021-39/
- https://www.mozilla.org/security/advisories/mfsa2021-40/
- https://www.mozilla.org/security/advisories/mfsa2021-41/
- https://www.mozilla.org/security/advisories/mfsa2021-42/
Affected products (3)
- cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
- cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
- cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
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