# CVE-2023-37580 — Synacor Zimbra Collaboration Suite **CISA KEV** > As of 2025-10-30, CVE-2023-37580 is a MEDIUM-severity vulnerability in Synacor Zimbra Collaboration Suite, CVSS v3.1 6.1, EPSS 49.0% (98.8th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-07-27), with a US federal remediation deadline of 2023-08-17. Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2023-37580, most recently “Zimbra Collaboration Suite Critical Stored XSS in Classic Web Client (Patched in ZCS 10.1.19)”. **Last updated:** 2025-10-30 ## What is CVE-2023-37580? Zimbra Collaboration (ZCS) 8 before 8.8.15 Patch 41 allows XSS in the Zimbra Classic Web Client. The record classifies CVE-2023-37580 under weakness class [CWE-79](https://intel.threadlinqs.com/cwe/CWE-79). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first. 14 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 1169 days ago. ## Severity and exploitation probability - **CVSS v3.1 base score:** 6.1 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`) - **EPSS (FIRST):** 49.0% probability of exploitation in the next 30 days, higher than 98.8% of all scored CVEs - **CISA KEV:** Listed since 2023-07-27, federal remediation deadline 2023-08-17 - **Threadlinqs priority:** 9/10 — CISA KEV-listed, which Threadlinqs floors at 9 - **Published:** 2023-07-31, last modified 2025-10-30 ## Is CVE-2023-37580 being exploited? CISA added CVE-2023-37580 to the Known Exploited Vulnerabilities catalog on 2023-07-27, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2023-08-17 under BOD 22-01. Weaponised exploit code for CVE-2023-37580 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (`http/cves/2023/CVE-2023-37580.yaml`). It currently carries a trending score of 50 in the Threadlinqs vulnerability feed. - [trickest/cve](https://github.com/trickest/cve/blob/main/2023/CVE-2023-37580.md) (trickest) ## Affected products and versions - [Synacor](https://intel.threadlinqs.com/vendors/synacor): Zimbra Collaboration Suite, Zimbra Collaboration Suite 8.8.15 _Showing 2 of 14 recorded product entries._ ## How to fix CVE-2023-37580 The record marks a vendor fix as available for CVE-2023-37580. Patch reference: [http://www.openwall.com/lists/oss-security/2023/11/17/2](http://www.openwall.com/lists/oss-security/2023/11/17/2). Because CVE-2023-37580 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2023-08-17. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory. ## Threat activity tracking CVE-2023-37580 1 tracked threat in the Threadlinqs corpus references CVE-2023-37580, either in the campaign’s CVE list or as an indicator on the campaign record. - [Zimbra Collaboration Suite Critical Stored XSS in Classic Web Client (Patched in ZCS 10.1.19)](https://intel.threadlinqs.com/threat/TL-2026-1176) — CRITICAL · 2026-07-10 ## Sources Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD. **Mailing list and disclosure** - [openwall.com — mailing list](http://www.openwall.com/lists/oss-security/2023/11/17/2) **Other references** - [wiki.zimbra.com](https://wiki.zimbra.com/wiki/Security_Center) - [wiki.zimbra.com (Zimbra Responsible Disclosure Policy)](https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy) Canonical: https://intel.threadlinqs.com/cve/CVE-2023-37580 Full detection coverage and IOCs for threats exploiting CVE-2023-37580 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp