How severe is CVE-2021-29945?

CVE-2021-29945 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 none, and availability high.

Is CVE-2021-29945 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-29945?

CVE-2021-29945 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-2021-29945?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-29945 published?

CVE-2021-29945 was published on 2021-06-24 and last updated on 2026-06-17.

CVE-2021-29945

CVE-2021-29945 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. The underlying weakness is classified as CWE-682.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (65th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-682
Affected product: Mozilla Firefox
Published: 2021-06-24
Last modified: 2026-06-17

Description

The WebAssembly JIT could miscalculate the size of a return type, which could lead to a null read and result in a crash. *Note: This issue only affected x86-32 platforms. Other platforms are unaffected.*. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

Frequently asked questions

What is CVE-2021-29945?: The WebAssembly JIT could miscalculate the size of a return type, which could lead to a null read and result in a crash. *Note: This issue only affected x86-32 platforms. Other platforms are unaffected.*. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.
How severe is CVE-2021-29945?: CVE-2021-29945 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 none, and availability high.
Is CVE-2021-29945 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-29945?: CVE-2021-29945 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-2021-29945?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-29945 published?: CVE-2021-29945 was published on 2021-06-24 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:x86:*
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:x86:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:x86:*

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