How severe is CVE-2021-28994?

CVE-2021-28994 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-28994 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28994?

CVE-2021-28994 primarily affects Kopano Groupware Core. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-28994?

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-2021-28994 published?

CVE-2021-28994 was published on 2021-03-31 and last updated on 2026-06-17.

CVE-2021-28994

CVE-2021-28994 is a high-severity vulnerability in Kopano Groupware Core 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (79th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-770
Affected product: Kopano Groupware Core
Published: 2021-03-31
Last modified: 2026-06-17

Description

kopano-ical (formerly zarafa-ical) in Kopano Groupware Core through 8.7.16, 9.x through 9.1.0, 10.x through 10.0.7, and 11.x through 11.0.1 and Zarafa 6.30.x through 7.2.x allows memory exhaustion via long HTTP headers.

Frequently asked questions

What is CVE-2021-28994?: kopano-ical (formerly zarafa-ical) in Kopano Groupware Core through 8.7.16, 9.x through 9.1.0, 10.x through 10.0.7, and 11.x through 11.0.1 and Zarafa 6.30.x through 7.2.x allows memory exhaustion via long HTTP headers.
How severe is CVE-2021-28994?: CVE-2021-28994 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-28994 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28994?: CVE-2021-28994 primarily affects Kopano Groupware Core. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-28994?: 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-2021-28994 published?: CVE-2021-28994 was published on 2021-03-31 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:kopano:groupware_core:*:*:*:*:*:*:*:*
cpe:2.3:a:zarafa:zarafa:*:*:*:*:*:*:*:*

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