How severe is CVE-2011-2991?

CVE-2011-2991 has a CVSS 2.0 base score of 10.0, rated critical severity.

Is CVE-2011-2991 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (90th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2011-2991?

CVE-2011-2991 primarily affects Mozilla Firefox. In total, 132 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2011-2991?

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

When was CVE-2011-2991 published?

CVE-2011-2991 was published on 2011-08-18 and last updated on 2026-06-16.

CVE-2011-2991

CVE-2011-2991 is a critical-severity vulnerability in Mozilla Firefox with a CVSS 2.0 base score of 10.0. 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-119.

Key facts

Severity: Critical (CVSS 2.0 base score 10.0)
EPSS exploit prediction: 4% (90th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: Mozilla Firefox
Published: 2011-08-18
Last modified: 2026-06-16

Description

The browser engine in Mozilla Firefox 4.x through 5, SeaMonkey 2.x before 2.3, Thunderbird before 6, and possibly other products does not properly implement JavaScript, which allows remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via unspecified vectors.

Frequently asked questions

What is CVE-2011-2991?: The browser engine in Mozilla Firefox 4.x through 5, SeaMonkey 2.x before 2.3, Thunderbird before 6, and possibly other products does not properly implement JavaScript, which allows remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via unspecified vectors.
How severe is CVE-2011-2991?: CVE-2011-2991 has a CVSS 2.0 base score of 10.0, rated critical severity.
Is CVE-2011-2991 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (90th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2011-2991?: CVE-2011-2991 primarily affects Mozilla Firefox. In total, 132 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2011-2991?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2011-2991 published?: CVE-2011-2991 was published on 2011-08-18 and last updated on 2026-06-16.

References

Affected products (132)

cpe:2.3:a:mozilla:firefox:4.0:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta1:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta10:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta11:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta12:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta2:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta3:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta4:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta5:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta6:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta7:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta8:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0:beta9:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:4.0.1:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:5.0:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.1:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.2:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.3:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.4:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.5:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.6:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.7:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.7.1:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.7.2:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.7.3:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.8:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:0.9:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.1:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.2:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.3:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.4:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.5:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.6:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.7:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.0.8:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.5:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.5:beta2:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:1.5.0.1:*:*:*:*:*:*:*

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