How severe is CVE-2026-33370?

CVE-2026-33370 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-33370 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33370?

CVE-2026-33370 affects Synacor Zimbra Collaboration Suite. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33370?

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

Does CVE-2026-33370 have an EU (EUVD) identifier?

Yes. CVE-2026-33370 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13694.

When was CVE-2026-33370 published?

CVE-2026-33370 was published on 2026-03-20 and last updated on 2026-06-17.

CVE-2026-33370

CVE-2026-33370 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite with a CVSS 3.x base score of 6.1. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13694
Weakness: CWE-79
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. A stored cross-site scripting (XSS) vulnerability exists in the Zimbra Briefcase feature due to insufficient sanitization of specific uploaded file types. When a user opens a publicly shared Briefcase file containing malicious scripts, the embedded JavaScript executes in the context of the user's session. This allows an attacker to run arbitrary scripts, potentially leading to data exfiltration or other unauthorized actions on behalf of the victim user.

Frequently asked questions

What is CVE-2026-33370?: An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Zimbra Briefcase feature due to insufficient sanitization of specific uploaded file types. When a user opens a publicly shared Briefcase file containing malicious scripts, the embedded JavaScript executes in the context of the user's session. This allows an attacker to run arbitrary scripts, potentially leading to data exfiltration or other unauthorized actions on behalf of the victim user.
How severe is CVE-2026-33370?: CVE-2026-33370 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-33370 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33370?: CVE-2026-33370 affects Synacor Zimbra Collaboration Suite. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33370?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-33370 have an EU (EUVD) identifier?: Yes. CVE-2026-33370 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13694.
When was CVE-2026-33370 published?: CVE-2026-33370 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:*:*:*:*:*:*:*:*

More vulnerabilities in Synacor Zimbra Collaboration Suite

CVE-2024-45519 — Critical (CVSS 10.0): The postjournal service in Zimbra Collaboration (ZCS) before 8.8.15 Patch 46, 9 before 9.0.0 Patch 41, 10 before…
CVE-2022-41352 — Critical (CVSS 9.8): An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0. An attacker can upload arbitrary files through…
CVE-2022-37042 — Critical (CVSS 9.8): Zimbra Collaboration Suite (ZCS) 8.8.15 and 9.0 has mboximport functionality that receives a ZIP archive and extracts…
CVE-2020-7796 — Critical (CVSS 9.8): Zimbra Collaboration Suite (ZCS) before 8.8.15 Patch 7 allows SSRF when WebEx zimlet is installed and zimlet JSP is…
CVE-2019-9670 — Critical (CVSS 9.8): mailboxd component in Synacor Zimbra Collaboration Suite 8.7.x before 8.7.11p10 has an XML External Entity injection…
CVE-2019-6980 — Critical (CVSS 9.8): Synacor Zimbra Collaboration Suite 8.7.x through 8.8.11 allows insecure object deserialization in the IMAP component.

All CVEs affecting Synacor Zimbra Collaboration Suite →

Other CWE-79 (Cross-site Scripting (XSS)) vulnerabilities

CVE-2025-49410 — Critical (CVSS 10.0): Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Imran Emu TC…
CVE-2024-47875 — Critical (CVSS 10.0): DOMPurify is a DOM-only, super-fast, uber-tolerant XSS sanitizer for HTML, MathML and SVG. DOMpurify was vulnerable to…
CVE-2024-6886 — Critical (CVSS 10.0): Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Gitea…
CVE-2023-45144 — Critical (CVSS 10.0): com.xwiki.identity-oauth:identity-oauth-ui is a package to aid in building identity and service providers based on…
CVE-2023-45138 — Critical (CVSS 10.0): Change Request is an pplication allowing users to request changes on a wiki without publishing the changes directly.…
CVE-2022-4361 — Critical (CVSS 10.0): Keycloak, an open-source identity and access management solution, has a cross-site scripting (XSS) vulnerability in the…

Browse all CWE-79 (Cross-site Scripting (XSS)) vulnerabilities →