How severe is CVE-2017-6821?

CVE-2017-6821 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2017-6821 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2017-6821?

CVE-2017-6821 affects Synacor Zimbra Collaboration Suite. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2017-6821?

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-2017-6821 published?

CVE-2017-6821 was published on 2017-05-23 and last updated on 2026-06-17.

CVE-2017-6821

CVE-2017-6821 is a critical-severity vulnerability in Synacor Zimbra Collaboration Suite with a CVSS 3.x base score of 9.8. 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-22.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 4% (89th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-22
Affected product: Synacor Zimbra Collaboration Suite
Published: 2017-05-23
Last modified: 2026-06-17

Description

Directory traversal vulnerability in Zimbra Collaboration Suite (aka ZCS) before 8.7.6 allows attackers to have unspecified impact via unknown vectors.

Frequently asked questions

What is CVE-2017-6821?: Directory traversal vulnerability in Zimbra Collaboration Suite (aka ZCS) before 8.7.6 allows attackers to have unspecified impact via unknown vectors.
How severe is CVE-2017-6821?: CVE-2017-6821 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2017-6821 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2017-6821?: CVE-2017-6821 affects Synacor Zimbra Collaboration Suite. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2017-6821?: 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-2017-6821 published?: CVE-2017-6821 was published on 2017-05-23 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*

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