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  • NetScaler WAF Signatures Update v117


    NetScaler Cyber Threat Intelligence
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    NetScaler WAF Signatures Update v117

    (limited to CISCO XE Software)

     

    NetScaler has released a new version of its integrated Web App Firewall signatures to help customers mitigate the maximum severity CVSS 10 zero-day vulnerability in Cisco IOS XE (CVE-2023-20198) which  has been exploited in the wild.

    Cisco has issued a security advisory regarding multiple vulnerabilities in the web UI feature of Cisco IOS XE Software. The most critical vulnerability, CVE-2023-20198, allows a remote, unauthenticated attacker to create an account on an affected system with privilege level 15 access. The attacker can then exploit another component of the web UI feature to elevate privilege to root and write the implant to the file system. Cisco has assigned a CVSS Score of 10.0 to CVE-2023-20198. The company is providing availability of Software Maintenance Upgrade (SMU) files and will update the advisory as additional releases post to Cisco Software Download Center. For steps to close the attack vector for these vulnerabilities, see the Recommendations section of Cisco's advisory. For protection until updating to latest version download and use v117 signature.

     

     Signatures included in v117:

    Signature rule

    CVE ID

    Description

    998597

    CVE-2023-20198

    WEB-MISC Cisco IOS XE Software - Authentication Bypass Vulnerability (CVE-2023-20198)

     

    NetScaler customers can quickly import the above signatures to help reduce risk and lower exposure associated with these vulnerabilities. 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 117 or later and then follow these steps.

    1. Search your signatures for <number>
    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 

    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. 

     

     

     

     

     


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