Ethical Hacking News
The Dutch National Cyber Security Centre is warning of a critical Citrix NetScaler flaw that was exploited by hackers to breach multiple organizations in the Netherlands. Organizations affected by this vulnerability are advised to upgrade their software immediately to prevent future breaches.
The Netherlands is facing a significant cybersecurity crisis due to a critical flaw in Citrix NetScaler software (CVE-2025-6543). Hackers have exploited the vulnerability to breach multiple organizations, resulting in severe operational disruption. Organizations are recommended to upgrade their software immediately to prevent future breaches. System administrators should scan devices for unusual PHP and XHTML files, as well as other IOCs, to detect potential threats.
The Netherlands is currently dealing with a significant cybersecurity crisis, as a critical flaw in the Citrix NetScaler software has been exploited by hackers, allowing them to breach critical organizations and organizations in the country. The vulnerability, tracked as CVE-2025-6543, is a memory overflow bug that can lead to unintended control flow or denial of service on impacted devices.
Citrix issued a bulletin about the flaw on June 25, 2025, warning that certain versions of their software were vulnerable to ongoing attacks. These included versions 14.1 before 14.1-47.46, 13.1 before 13.1-59.19, and 13.1-FIPS and 13.1-NDcPP before 13.1-37.236. Furthermore, the Citrix advisory explains that memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.
The National Cyber Security Centre (NCSC) of the Netherlands has confirmed that hackers have leveraged the flaw to breach multiple entities in the country. The NCSC's warning now indicates that attackers exploited this vulnerability for remote code execution. The attacks occurred since at least early May, nearly two months before Citrix published its bulletin and made patches available, so they were exploited as zero days for an extended period.
According to the NCSC, these attacks resulted in severe operational disruption for some of the impacted organizations. Some of these organizations gradually returned online and fired up their email servers only last week. It is unclear whether Citrix Bleed 2 was also abused in attacks or if it's the same update process for both flaws.
The NCSC has determined that multiple critical organizations in the Netherlands have been successfully attacked via a vulnerability identified as CVE-2025-6543 in Citrix NetScaler, resulting from the work of one or more actors with an advanced modus operandi. The attackers exploited this vulnerability as a zero-day attack and actively removed traces to conceal compromise at affected organizations.
In order to address the risk from CVE-2025-6543, organizations are recommended to upgrade to NetScaler ADC and NetScaler Gateway 14.1 version 14.1-47.46 and later, version 13.1-59.19 and later, and ADC 13.1-FIPS and 13.1-NDcPP version 13.1-37.236 and later.
System administrators are also advised to look for signs of compromise such as an atypical file creation date, duplicate file names with different extensions, and the absence of PHP files in the folders. The cybersecurity agency has also released a script on GitHub that can scan devices for unusual PHP and XHTML files, as well as other IOCs.
The NCSC's determination confirms that hackers have leveraged this vulnerability to breach multiple organizations in the Netherlands, resulting from a zero-day attack where attackers exploited the flaw to achieve remote code execution. It is now known that some critical organizations suffered severe operational disruption following an attack via this vulnerability identified as CVE-2025-6543.
To further prevent future breaches of similar vulnerabilities, system administrators and organizations are advised to upgrade their software immediately and implement measures such as scanning devices for unusual PHP and XHTML files, as well as other IOCs.
Furthermore, it is recommended that system administrators look out for signs of compromise such as an atypical file creation date, duplicate file names with different extensions, and the absence of PHP files in folders. The NCSC has also released a script on GitHub to scan devices for unusual PHP and XHTML files, as well as other IOCs.
In summary, a critical flaw in Citrix NetScaler software, tracked as CVE-2025-6543, was exploited by hackers to breach multiple organizations in the Netherlands, resulting in severe operational disruption. To address this risk, organizations are recommended to upgrade their software immediately and implement measures such as scanning devices for unusual PHP and XHTML files, as well as other IOCs.
The Netherlands is facing a significant cybersecurity crisis due to a critical flaw in Citrix NetScaler that was exploited by hackers to breach multiple organizations. Organizations affected by this vulnerability are advised to upgrade their software immediately to prevent future breaches.
Related Information:
https://www.ethicalhackingnews.com/articles/Netherlands-Faces-Citrix-Netscaler-Cybersecurity-Crisis-How-a-Critical-Flaw-Exposed-Orgs-to-Breaches-ehn.shtml
https://www.bleepingcomputer.com/news/security/netherlands-citrix-netscaler-flaw-cve-2025-6543-exploited-to-breach-orgs/
Published: Mon Aug 11 15:22:24 2025 by llama3.2 3B Q4_K_M
