How severe is CVE-2021-3964?

CVE-2021-3964 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-3964 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3964?

CVE-2021-3964 affects Elgg. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3964?

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

When was CVE-2021-3964 published?

CVE-2021-3964 was published on 2021-12-01 and last updated on 2026-06-17.

CVE-2021-3964

CVE-2021-3964 is a medium-severity vulnerability in Elgg with a CVSS 3.x base score of 5.9. 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-639.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
CVSS v2: 4.3
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-639
Affected product: Elgg
Published: 2021-12-01
Last modified: 2026-06-17

Description

elgg is vulnerable to Authorization Bypass Through User-Controlled Key

Frequently asked questions

What is CVE-2021-3964?: elgg is vulnerable to Authorization Bypass Through User-Controlled Key
How severe is CVE-2021-3964?: CVE-2021-3964 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-3964 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3964?: CVE-2021-3964 affects Elgg. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3964?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3964 published?: CVE-2021-3964 was published on 2021-12-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:elgg:elgg:*:*:*:*:*:*:*:*

More vulnerabilities in Elgg

CVE-2011-2936 — Critical (CVSS 9.8): Elgg through 1.7.10 has a SQL injection vulnerability
CVE-2021-3980 — High (CVSS 7.5): elgg is vulnerable to Exposure of Private Personal Information to an Unauthorized Actor
CVE-2012-6562 — Medium (CVSS 6.8): engine/lib/users.php in Elgg before 1.8.5 does not properly specify permissions for the useradd action, which allows…
CVE-2011-2935 — Medium (CVSS 6.1): Elgg through 1.7.10 has XSS
CVE-2019-11016 — Medium (CVSS 6.1): Elgg before 1.12.18 and 2.3.x before 2.3.11 has an open redirect.
CVE-2021-4072 — Medium (CVSS 5.4): elgg is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

All CVEs affecting Elgg →

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