CVE-2025-27915
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA stored cross-site scripting (XSS) vulnerability exists in Zimbra Collaboration's Classic Web Client where ICS (iCalendar) files embedded in email messages are not properly sanitized. Attackers can embed malicious JavaScript via an ontoggle event inside a <details> tag, which executes when the user views the email, allowing session hijack and unauthorized account actions.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 10.0.0, < 10.0.13>= 10.1.0, < 10.1.5= 9.0.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Zimbra Collaboration Suite versionRun 'zmcontrol -v' as the zimbra user or check /opt/zimbra/.gitdescribe to determine the installed versionAffected if Version is 9.0.0, or 10.0.0 through 10.0.12, or 10.1.0 through 10.1.4 (falls within the affected ranges)
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Confirm Classic Web Client is enabledCheck Zimbra admin console under Class of Service or verify client access URL contains '/zimbra/' rather than '/zimbra-new/' to identify if Classic Web Client is in useAffected if Classic Web Client is the active interface (the vulnerability is specific to Classic, not Modern, web client)
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Verify email ICS attachment handling is activeReview Zimbra mail store configuration for ICS MIME type handling and ensure mail preview/rendering features for calendar attachments are enabledAffected if ICS attachments in emails are being processed and rendered by the web client (required for the XSS to trigger)
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Inspect for malicious ICS content in mailboxesSearch mailbox database or use Zimbra search for ICS attachments containing '<details' tags or 'ontoggle' event handlers in email messagesAffected if ICS attachments with embedded <details> tags containing ontoggle event handlers are present in any user mailbox
Environment is affected if running a vulnerable Zimbra version (9.0.0, 10.0.x before 10.0.13, or 10.1.x before 10.1.5) with Classic Web Client and ICS attachment processing enabled, allowing stored XSS via malicious ICS content.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped10.0.1310.1.5
Apply vendor-supplied patches for CVE-2025-27915. Until patched, users should avoid opening ICS content from untrusted senders, and administrators may consider disabling ICS attachment preview functionality in the Classic Web Client.
Zimbra 10.0.x → 10.0.13+; Zimbra 10.1.x → 10.1.5+; Zimbra 9.0.0 → latest 9.x patch or migrate to 10.x
- 1. Identify the current Zimbra Collaboration Suite version by checking the Admin Console or running 'zmcontrol -v'
- 2. For Zimbra 10.0.x installations (versions 10.0.0 through 10.0.12): Upgrade to version 10.0.13 or later
- 3. For Zimbra 10.1.x installations (versions 10.1.0 through 10.1.4): Upgrade to version 10.1.5 or later
- 4. For Zimbra 9.0.0: Upgrade to the latest 9.0.0 patch or migrate to a supported 9.x or 10.x version per Zimbra's support lifecycle
- 5. After upgrade, verify the fix by testing ICS file import with crafted HTML content in the Classic Web Client
- 6. Consider disabling the Classic Web Client and using the Modern Web Client as a temporary mitigation if immediate upgrade is not feasible
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-27915 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-27915 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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- Version or environment caveats, and links to real fixes
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