NetScaler WAF mitigates risk from Zimbra XSS vulnerability 

NetScaler has new signatures available for its integrated Web App Firewall to help customers mitigate the recent critical cross site scripting vulnerability in Zimbra Collaboration Suite (ZCS) v.8.8.15, Zimbra Classic Web Client version 8 before 8.8.15 Patch 41 and Zimbra Collaboration ZCS v.8.8.15 and v.9.0 . 

The new signatures protect customers from the recent CVE-2023-34192, CVE-2023-29382, CVE-2023-37580 vulnerabilities that allow XSS and arbitrary code execution.

The aforementioned vulnerabilities are classed as critical. Customers should apply the latest NetScaler WAF signature file to help mitigate exploitation of this vulnerability in their environments.You can download the signatures and apply them immediately.  

Mitigations:

CVE-2023-34192

The NIST database has details about the vulnerability:

Cross Site Scripting vulnerability in Zimbra ZCS v.8.8.15 allows a remote authenticated attacker to execute arbitrary code via a crafted script to the /h/autoSaveDraft function.

CVE-2023-29382

The NIST database has details about the vulnerability:

An issue in Zimbra Collaboration ZCS v.8.8.15 and v.9.0 allows an attacker to execute arbitrary code via the sfdc_preauth.jsp component.

CVE-2023-37580

The NIST database has details about the vulnerability:

Zimbra Collaboration (ZCS) 8 before 8.8.15 Patch 41 allows XSS in the Zimbra Classic Web Client.

The vendor (Zimbra) recommends that users of Zimbra Collaboration Suite Version 8.8.15 immediately adhere to their published mitigation measures and apply the appropriate patch to the software in order to prevent exploitation of these vulnerabilities. 

NetScaler customers can quickly implement the  following recommendations to help reduce risk and lower exposure associated with this vulnerability. If you are using any of the affected MOVEit Transfer  versions, NetScaler strongly recommends that you download the version 111 or later of the signature file and apply it to your NetScaler Web App Firewall deployments as an additional layer of protection for your applications.  Signatures are compatible with NetScaler (formerly Citrix ADC) software version 11.1, 12.0, 12.1, 13.0 and 13.1. NOTE: software versions 11.1 and 12.0 are end of life and you should consider upgrading for continued support. Learn more about the NetScaler software release lifecycle.

If you are already using NetScaler Web App Firewall with the signature auto-update feature enabled, verify that your signature file version is 111 or later and then follow these steps.

1. Search your signatures for CVE-2023-37580, CVE-2023-34192, CVE-2023-29382 LogString
2. Select the results with ID 
3. Choose “Enable Rules” and click OK

NetScaler WAF Best Practices

NetScaler recommends that WAF users always download the latest signature version, enable signature auto-update, and subscribe to receive signature alert notifications. NetScaler will continue to monitor this dynamic situation and provide updates as new mitigations become available.

Handling false positives

If app availability is affected by false positives that result from the above mitigation policies, relaxations can be applied. NetScaler recommends the following modifications to the policy.

Modifications to NetScaler Web App Firewall Policy:

add policy patset exception_list

# (Example: bind policy patset exception_list “/exception_url”) 

Prepend the existing WAF policy with:

HTTP.REQ.URL.CONTAINS_ANY(“exception_list”).NOT

# (Example :  set appfw policy my_WAF_policy q^HTTP.REQ.URL.CONTAINS_ANY(“exception_list”).NOT && <existing rule>^

NOTE: Any endpoint covered by the exception_list may expose those assets to risks from CVE-2023-37580, CVE-2023-34192, CVE-2023-29382.

Additional Information

NetScaler Web App Firewall benefits from a single code base across all its form-factors (physical, virtual, bare-metal, and containers). This signature update applies to all form factors and deployment models of NetScaler Web App Firewall.

Learn more about NetScaler Web app Firewall, read our alert articles and bot signature articles to learn more about NetScaler WAF signatures, and find out how you can receive signature alert notifications.

Please join the NetScaler Community today and engage with your peers to learn more about how they are protecting their businesses with NetScaler WAF.