How severe is CVE-2026-33371?

CVE-2026-33371 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2026-33371 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33371?

CVE-2026-33371 affects Synacor Zimbra Collaboration Suite. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33371?

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

Does CVE-2026-33371 have an EU (EUVD) identifier?

Yes. CVE-2026-33371 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13696.

When was CVE-2026-33371 published?

CVE-2026-33371 was published on 2026-03-20 and last updated on 2026-06-17.

CVE-2026-33371

CVE-2026-33371 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite with a CVSS 3.x base score of 4.3. 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-611.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13696
Weakness: CWE-611
Affected product: Synacor Zimbra Collaboration Suite
Published: 2026-03-20
Last modified: 2026-06-17

Description

An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. An XML External Entity (XXE) vulnerability exists in the Zimbra Exchange Web Services (EWS) SOAP interface due to improper handling of XML input. An authenticated attacker can submit crafted XML data that is processed by an XML parser with external entity resolution enabled. Successful exploitation may allow disclosure of sensitive local files from the server.

Frequently asked questions

What is CVE-2026-33371?: An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. An XML External Entity (XXE) vulnerability exists in the Zimbra Exchange Web Services (EWS) SOAP interface due to improper handling of XML input. An authenticated attacker can submit crafted XML data that is processed by an XML parser with external entity resolution enabled. Successful exploitation may allow disclosure of sensitive local files from the server.
How severe is CVE-2026-33371?: CVE-2026-33371 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2026-33371 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33371?: CVE-2026-33371 affects Synacor Zimbra Collaboration Suite. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33371?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-33371 have an EU (EUVD) identifier?: Yes. CVE-2026-33371 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13696.
When was CVE-2026-33371 published?: CVE-2026-33371 was published on 2026-03-20 and last updated on 2026-06-17.

References

Affected products (1)

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

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