CVE-2026-73571: CVE-2026-73571: An authorization bypass vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.17 …
synacor · zimbra collaboration suite · NVD published 2026-08-13 · posted 2026-08-13 · last modified 2026-08-28
CVE-2026-73571 at a glance
CVE-2026-73571 is a medium-severity Authorization Bypass vulnerability in Synacor Zimbra Collaboration Suite, with a CVSS 3.1 base score of 4.3. NVD published it on 2026-08-13 and classifies the weakness as CWE-863. Public exploit code: 1 Metasploit module, with the earliest exploit evidence dated 2026-08-13. FIRST EPSS puts the probability of exploitation activity in the next 30 days at 0.63% (percentile 50.8, scored 2026-11-14). NVD configuration data lists a fixed release for 1 product, for example synacor zimbra collaboration suite 10.1.17. CVERadar maps 1 MITRE ATT&CK technique across Privilege Escalation, inferred from the CWE and the description. Its CVERadar threat level is 32/100.
What it is
An authorization bypass vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.17 due to improper authorization validation in delegated email sending functionality. An authenticated attacker can send specially crafted SOAP requests to impersonate another user and send emails without possessing the required delegation or send-as permissions. This occurs in the SaveDraftRequest SOAP handler.
| Weakness | CWE-863 definition |
|---|---|
| CVSS vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N (source: NIST NVD) |
| ATT&CK tactics | Privilege Escalation |
Exploitation evidence
First exploit evidence seen: 2026-08-13 (earliest date across the sources below).
Exploited in the wild
No source on this site lists in-the-wild exploitation yet (CISA KEV, VulnCheck KEV).
Public exploit code
Metasploit
- Metasploit module auxiliary/admin/http/zimbra_email_impersonation: Zimbra SaveDraftRequest Email Impersonation (disclosure 2026-08-13)
Sources: Rapid7 Metasploit Framework module metadata.
Defend the Chain
The attack chain for CVE-2026-73571 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.
Pick a red technique card on the board, then choose the defence that stops it.
Defend against T1068 Exploitation for Privilege Escalation Inferred
Inferred from CWE CWE-863
Patches, mitigations and detection
Fixed versions
- synacor zimbra collaboration suite: upgrade to 10.1.17 or later
Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.
Vendor advisories and patches
- Vendor advisory (wiki.zimbra.com) (Vendor Advisory)
- Vendor advisory (wiki.zimbra.com) (Vendor Advisory)
MITRE ATT&CK mitigations for this chain
- M1051 Update Software (for T1068) : Update software regularly by employing patch management for internal enterprise endpoints and servers.
- M1050 Exploit Protection (for T1068) : Security applications that look for behavior used during exploitation such as Windows Defender Exploit Guard (WDEG) and the Enhanced Mitigation Experience Toolkit (EMET) can be used to mitigate some exploitation behavior. Control flow integrity checking is another way to potentially identify and stop a software exploi
- M1048 Application Isolation and Sandboxing (for T1068) : Make it difficult for adversaries to advance their operation through exploitation of undiscovered or unpatched vulnerabilities by using sandboxing. Other types of virtualization and application microsegmentation may also mitigate the impact of some types of exploitation. Risks of additional exploits and weaknesses in t
- M1019 Threat Intelligence Program (for T1068) : Develop a robust cyber threat intelligence capability to determine what types and levels of threat may use software exploits and 0-days against a particular organization.
- M1038 Execution Prevention (for T1068) : Consider blocking the execution of known vulnerable drivers that adversaries may exploit to execute code in kernel mode. Validate driver block rules in audit mode to ensure stability prior to production deployment.
Detection Generic guidance
- Privilege Escalation: Alert on processes gaining SYSTEM/root unexpectedly, and on exploitation crashes of privileged services.
Response checklist Generic guidance
- Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
- Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
- Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
- Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.
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