How severe is CVE-2021-29952?

CVE-2021-29952 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-29952 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-29952?

CVE-2021-29952 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-29952?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-29952 published?

CVE-2021-29952 was published on 2021-06-24 and last updated on 2026-06-17.

CVE-2021-29952

CVE-2021-29952 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-362.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.1
EPSS exploit prediction: 1% (50th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-362
Affected product: Mozilla Firefox
Published: 2021-06-24
Last modified: 2026-06-17

Description

When Web Render components were destructed, a race condition could have caused undefined behavior, and we presume that with enough effort may have been exploitable to run arbitrary code. This vulnerability affects Firefox < 88.0.1 and Firefox for Android < 88.1.3.

Frequently asked questions

What is CVE-2021-29952?: When Web Render components were destructed, a race condition could have caused undefined behavior, and we presume that with enough effort may have been exploitable to run arbitrary code. This vulnerability affects Firefox < 88.0.1 and Firefox for Android < 88.1.3.
How severe is CVE-2021-29952?: CVE-2021-29952 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-29952 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-29952?: CVE-2021-29952 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-29952?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-29952 published?: CVE-2021-29952 was published on 2021-06-24 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:-:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:android:*:*

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Other CWE-362 (Race Condition) vulnerabilities

CVE-2022-27626 — Critical (CVSS 10.0): A vulnerability regarding concurrent execution using shared resource with improper synchronization ('Race Condition')…
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CVE-2014-0703 — Critical (CVSS 10.0): Cisco Wireless LAN Controller (WLC) devices 7.4 before 7.4.110.0 distribute Aironet IOS software with a race condition…
CVE-2010-1228 — Critical (CVSS 10.0): Multiple race conditions in the sandbox infrastructure in Google Chrome before 4.1.249.1036 have unspecified impact and…
CVE-2008-6598 — Critical (CVSS 10.0): Multiple race conditions in WANPIPE before 3.3.6 have unknown impact and attack vectors related to "bri restart logic."
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