CVE-2026-93631
HIGH 7.1A cross-site request forgery vulnerability in the OAuth extension of Zimbra Collaboration Suite (ZCS) Network Edition allows an attacker to link an attacker-controlled external account to a victim's mailbox. The OAuth callback does not bind its state value or authorization code to the initiating Zimbra session and instead selects the destination mailbox from the browser's current authentication cookie. On a deployment with the provider configured, an attacker can induce a signed-in victim to load a callback containing a fresh code for the attacker's provider account. This creates a persistent data source that imports attacker-controlled contacts or events. With bidirectional CalDAV synchronization, appointments subsequently created or edited in the linked calendar are also disclosed to the attacker. ZCS 10.1.16 and 10.1.20 are affected.
Severe if exploited (CVSS 7.1), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.1%chance of exploitation in 30 days · 4th percentile
Impact if exploited
7.1CVSS 3.1 · HIGH
- ConfidentialityHigh
- IntegrityLow
- AvailabilityNone
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ⚠User interaction: A user must take an action (click / open a file)
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Data snapshot:
Weakness (CWE)
- CWE-352: Cross-Site request forgery (CSRF)
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
References and research data (JSON)
All CVSS metrics
- HIGH 7.1 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N - HIGH 7.1 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
References
Advisories
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories CVE record · rapid7 · Updated 2026-10-23T13:23:34.952Z
NVD · CVE-2026-93631 · Updated 2026-10-23T16:44:17.950 - https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-108972 EUVD · EUVD-2026-108972
Technical & other
- https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ CVE record · rapid7 · Updated 2026-10-23T13:23:34.952Z
NVD · CVE-2026-93631 · Updated 2026-10-23T16:44:17.950