CVE-2025-27915
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a <details> tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? Yes. Cross-site scripting sends script tags or event handlers in the request, which WAF signatures match well.
Also consider: CSP · output encoding
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2025-27915 being exploited?
Yes. CVE-2025-27915 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2025-27915?
CVE-2025-27915 is rated Medium with a CVSS score of 5.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-27915?
Yes. A fix has been recorded for CVE-2025-27915. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-27915 affect?
CVE-2025-27915 affects synacor:zimbra_collaboration_suite. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
public exploits
Detection templates only, no public exploit found: 1 Nuclei template
- Zimbra - Cross-Site Scripting via ICS Files · detection template · medium
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 7 Oct 2025 (SSVC 2.0.3).
timeline
- 12 Mar 2025Published
- 7 Oct 2025Added to CISA KEV (exploited in the wild) · 208 days (about 7 months) later
- 7 Oct 2025CISA SSVC assessment: exploitation active · same day later
- 28 Oct 2025CISA remediation due date (US federal agencies) · 21 days later
- 26 Feb 2026CVE record last updated · 122 days (about 4 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 249 days (about 8 months) later
- Linkwiki.zimbra.com /wiki/Security_Center
- Linkwiki.zimbra.com /wiki/Zimbra_Releases/10.1.5#Security_Fixes
- Linkwiki.zimbra.com /wiki/Zimbra_Releases/10.0.13#Security_Fixes
- Linkwiki.zimbra.com /wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes
- Linkstrikeready.com /blog/0day-ics-attack-in-the-wild/
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-27915
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Nuclei templates: detection templates
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.