CVE-2023-4966

ulnerability and there are signs of in-the-wild exploitation already. The new memory overread vulnerability, tracked as CVE-2026-8451, was found by researchers from security firm watchTowr who published a detailed write-up showing how unauthenticated malformed requests can result in protected process memory data being leaked back in responses. The ori

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) adds a flaw in Citrix NetScaler to its Known Exploited Vulnerabilities catalog. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added a flaw in Citrix NetScaler, tracked as CVE-2026-3055 (CVSS ver. 4.0 score of 9.3), to its Known Exploited Vulnerabilities (KEV) catalog. In March, Citrix issued security updates for two NetScaler vulnerabilities, […]

Attackers are actively probing a critical Citrix NetScaler flaw (CVE-2026-3055) that can leak sensitive data via a memory overread issue. A critical vulnerability, tracked as CVE-2026-3055 (CVSS score of 9.3), in Citrix NetScaler ADC and Gateway is already being actively probed by attackers. This week, Citrix issued security updates for two NetScaler vulnerabilities, including the critical memory […]

Citrix warns of a critical NetScaler flaw (CVE-2026-3055) that could leak sensitive data; users are urged to apply security updates immediately. Citrix issued security updates for two NetScaler vulnerabilities, including a critical memory overread, tracked as CVE-2026-3055 (CVSS score of 9.3), that allows unauthenticated attackers to leak sensitive data. The flaw CVE-2026-3055 is an insufficient […]

loits were used or suspected, the threat actors targeted vulnerabilities in common VPNs and firewalls such as Fortinet (CVE-2024-55591, CVE-2024-21762, and CVE-2019-6693), SonicWall (CVE-2024-40766), Palo Alto (CVE-2024-3400), and Citrix (CVE-2023-4966). We also observed malicious actors successfully exploit a variety of other exposed services, includi

Amazon has seen a threat actor exploiting CVE-2025-20337 and CVE-2025-5777, two critical Cisco and Citrix vulnerabilities, as zero-days.

CISA considers the recently disclosed CitrixBleed 2 vulnerability an unacceptable risk and has added it to the KEV catalog.

U.S. Cybersecurity and Infrastructure Security Agency (CISA) adds Citrix NetScaler ADC and Gateway flaw to its Known Exploited Vulnerabilities catalog. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added Citrix NetScaler ADC and Gateway flaw, tracked as CVE-2025-5777, to its Known Exploited Vulnerabilities (KEV) catalog. The CVE-2025-5777 flaw, dubbed ‘CitrixBleed 2‘ (CVSS v4.0 Base Score of 9.3), […]

Security researchers have released a technical analysis and proof-of-concept exploit code for a critical vulnerability fixed last month in Citrix NetScaler appliances that is suspected to have been exploited in the wild, though in a limited capacity and without official confirmation from Citrix. Companies are urged to deploy the patches and use published indicators of […]

Researchers released technical information and exploit code targeting a critical vulnerability (CVE-2025-5777) in Citrix NetScaler.

Background and Confusion On June 17, 2025, Citrix published an advisory detailing CVE-2025-5777 and CVE-2025-5349. Affected products include: On June 25, 2025, they also published an advisory detailing CVE-2025-6543. Affected products include: Of the three vulnerabilities, two of them have been receiving a bit of buzz: While we’ve developed a working exploit for one of […]

Many Citrix NetScaler systems are exposed to attacks exploiting the vulnerabilities tracked as CVE-2025-5777 and CVE-2025-6543.

While Citrix has observed some instances where CVE-2025-6543 has been exploited on vulnerable NetScaler networking appliances, the company still says that they don’t have evidence of exploitation for CVE-2025-5349 or CVE-2025-5777, both of which have been patched earlier this month. CVE-2025-5777, in particular, has captured the attention of infosec professionals due to its similarity to CVE-2023-4966, aka CitrixBleed. Consequently, CVE-2025-5777 has been informally dubbed “CitrixBleed 2” by security researcher Kevin Beaumont. Both CitrixBleed and CitrixBleed … More →

The Citrix NetScaler vulnerability tracked as CitrixBleed 2 and CVE-2025–5777 may be exploited in the wild for initial access.

New Citrix flaw ‘CitrixBleed 2’ lets attackers steal session cookies without logging in, echoing a previously exploited vulnerability. A new flaw in Citrix NetScaler ADC and Gateway, dubbed ‘CitrixBleed 2‘ (CVE-2025-5777, CVSS v4.0 Base Score of 9.3), can allow unauthenticated attackers to steal session cookies, similar to a past critical exploit. The vulnerability is an […]

Citrix has fixed a critical vulnerability (CVE-2025-5777) in NetScaler ADC and NetScaler Gateway reminiscent of the infamous and widely exploited CitrixBleed flaw. The vulnerabilities have been privately disclosed and there is no indication that they are under active exploitation. Nevertheless, the company has urged to install the relevant updated versions as soon as possible and terminate active sessions. About the vulnerabilities (CVE-2025-5777, CVE-2023-4966) CVE-2025-5777 is an out-of-bounds read flaw stemming from insufficient input validation. Like … More →

Ivanti is warning customers that a critical vulnerability that impacts its VPN appliances and other products has already been exploited in the wild by a Chinese APT group. The flaw was originally flagged by Ivanti as a denial-of-service issue, but attackers figured out how to exploit it for remote code execution. The vulnerability, now tracked […]

A suspected Chinese APT group has exploited CVE-2025-22457 – a buffer overflow bug that was previously thought not to be exploitable – to compromise appliances running Ivanti Connect Secure (ICS) 22.7R2.5 or earlier or Pulse Connect Secure 9.1x. The vulnerability was patched by Ivanti in ICS 22.7R2.6, released on February 11, 2025. But, apparently, the threat actor studied the patch and “uncovered through a complicated process, [that] it was possible to exploit 22.7R2.5 and earlier … More →

Most of the top frequently exploited vulnerabilities in 2023 were initially exploited as zero-days, according to data from government agencies.

A threat actor has been compromising the hybrid cloud environments of US organizations in multiple sectors.

Government agencies in the US, New Zealand, and Canada have published new guidance on improving network security.

A critical vulnerability has been affecting a line of Citrix NetScaler appliances, allowing attackers to capture sensitive information from the devices’ memory, but is now fixed, according to a Bishop Fox research. The vulnerability, which Citrix now appears to have silently addressed, was identified within Citrix NetScaler ADC and Gateway, affecting the devices running version […]

Analysis of ransomware gang leak site data reveals significant activity over 2023. As groups formed — or dissolved — and tactics changed, we synthesize our findings.

Citrix fixed two actively exploited zero-day vulnerabilities impacting Netscaler ADC and Gateway appliances. Citrix warns customers to install security updates to address two actively exploited zero-day vulnerabilities, tracked as CVE-2023-6548 and CVE-2023-6549, impacting Netscaler ADC and Gateway appliances. “Exploits of these CVEs on unmitigated appliances have been observed. Cloud Software Group strongly urges affected customers […]

For the latest discoveries in cyber research for the week of 25th December, please download our Threat_Intelligence Bulletin. TOP ATTACKS AND BREACHES Australia’s largest non-profit healthcare provider, St. Vincent’s Health Australia, experienced a cyberattack resulting in data theft from its networks. Vincent’s operates public and private hospitals, as well as elderly care facilities across New […]

The recently disclosed Xfinity data breach, which involved exploitation of the CitrixBleed vulnerability, impacts 36 million individuals

Telecommunications company Comcast has confirmed a breach that exposed personal information of more than 35.8 million of Xfinity customers. Exploiting Citrix Bleed to breach Xfinity CVE-2023-4966 (aka Citrix Bleed) – an information disclosure vulnerability in Citrix NetScaler ADC/Gateway devices – was disclosed on October 10, when Citrix issued a patch to fix the vulnerability. (CVE-2023-4966 has been exploited as a zero-day by attackers since late August 2023, and

Comcast’s Xfinity discloses a data breach after a cyber attack hit the company by exploiting the CitrixBleed vulnerability. Comcast’s Xfinity is notifying its customers about the compromise of their data in a cyberattack that involved the exploitation of the CitrixBleed flaw. CitrixBleed is a critical vulnerability, tracked as CVE-2023-4966, in Citrix NetScaler ADC (Application Delivery […]

Comcast’s residential cable unit, Xfinity, has been hit by a cybersecurity breach in which hackers exploiting a critical vulnerability dubbed Citrix Bleed accessed the confidential information of nearly 36 million customers. The vulnerability is embedded in certain Citrix networking devices that are widely used across major corporations. Citrix responded with patches in early October, but […]

Comcast’s Xfinity says customer data, including credentials, were compromised in an attack exploiting the CitrixBleed vulnerability

For the latest discoveries in cyber research for the week of 4th December, please download our Threat_Intelligence Bulletin. TOP ATTACKS AND BREACHES Check Point Research provides highlights about Cyber Av3ngers group activity, which has taken responsibility on defacing workstations at Pennsylvania’s Aliquippa municipal water authority. Following the attack, CISA has published an advisory about this […]

The cyber attack that hit the managed service provider (MSP) CTS potentially impacted hundreds in the United Kingdom. CTS is a trusted provider of IT services to the legal sector in the UK. The company announced that it is investigating a cyber attack that caused a service outage. The incident impacted a portion of the […]

Here’s an overview of some of last week’s most interesting news, articles, interviews and videos: PolarDNS: Open-source DNS server tailored for security evaluations PolarDNS is a specialized authoritative DNS server that allows the operator to produce custom DNS responses suitable for DNS protocol testing purposes. Open-source AV/EDR bypassing lab for training and learning Best EDR Of The Market is a user-mode endpoint detection and response (EDR) project designed to serve as a testing ground for … More →

CVE-2023-4966, aka “Citrix Bleed”, has been exploited by LockBit 3.0 affiliates to breach Boeing’s parts and distribution business, and “other trusted third parties have observed similar activity impacting their organization,” cybersecurity and law enforcement officials have confirmed on Tuesday. In a joint cybersecurity advisory, the Cybersecurity and Infrastructure Security Agency (CISA), the FBI and officials from the Australian Cyber Security Center (ACSC) have shared the tactics, techniques, and procedures and indicators of compromise (IoCs) shared … More →

Administrators are urged to patch the recent CitrixBleed NetScaler vulnerability as LockBit starts exploiting it.

Citrix urges admins to kill NetScaler user sessions after patching their appliances against the CVE-2023-4966 Citrix Bleed vulnerability. Citrix is providing additional measures to admins who are patching their NetScaler appliances against the CVE-2023-4966 ‘Citrix Bleed‘ vulnerability. The company is urging admins to drop all active user sessions and terminate all persistent ones. “If you […]

Toyota Financial Services has been hit by a ransomware attack that may have involved exploitation of the CitrixBleed vulnerability.

The LockBit ransomware group published data allegedly stolen from the aerospace giant Boeing in a recent attack. The Boeing Company, commonly known as Boeing, is one of the world’s largest aerospace manufacturers and defense contractors. In 2022, Boeing recorded $66.61 billion in sales, the aerospace giant has 156,000 (2022). At the end of October, the Lockbit ransomware […]

The state-owned Industrial and Commercial Bank of China (ICBC), which is one of the largest banks in the world, has been hit by a ransomware attack that led to disrupted trades in the US Treasury market. The attack “On November 8, 2023, U.S. Eastern Time (November 9, 2023, Beijing Time), ICBC Financial Services (FS) experienced a ransomware attack that resulted in disruption to certain FS systems. Immediately upon discovering the incident, ICBC FS disconnected and … More →

The Industrial and Commercial Bank of China (ICBC) suffered a ransomware attack that disrupted trades in the US Treasury market. The Industrial and Commercial Bank of China (ICBC) announced it has contained a ransomware attack that disrupted the U.S. Treasury market and impacted some fixed income and equities transactions “The Securities Industry and Financial Markets […]

Here’s an overview of some of last week’s most interesting news, articles, interviews and videos: AI threat landscape: Model theft and inference attacks emerge as top concerns In this Help Net Security interview, Guy Guzner, CEO at Savvy, discusses the challenges and opportunities presented by in-house AI models, the security landscape surrounding them, and the future of AI cybersecurity. A closer look at healthcare’s battle with AI-driven attacks In this Help Net Security interview, Troy … More →

Threat brief on CVE-2023-4966 (aka Citrix Bleed) affecting multiple Netscaler products covers attack scope, threat hunting queries and interim guidance.

Multiple threat actors are exploiting CVE-2023-4966, aka Citrix Bleed, a critical vulnerability in NetScaler ADC and Gateway.

CVE-2023-4966, aka “Citrix Bleed”, a critical information disclosure vulnerability affecting Citrix NetScaler ADC/Gateway devices, is being massively exploited by threat actors. According to security researcher Kevin Beaumont’s cybersecurity industry sources, one ransomware group has already distributed a Python script to automate the attack chain to their operators, and other groups have started leveraging a working exploit. CVE-2023-4966 exploited Threat actors have been quick to leverage vulnerabilities in Citrix NetScaler ADC in the past, and this … More →

A new round of the weekly SecurityAffairs newsletter arrived! Every week the best security articles from Security Affairs are free for you in your email box. Enjoy a new round of the weekly SecurityAffairs newsletter, including the international press. Bug hunters earned $1,038,250 for 58 unique 0-days at Pwn2Own Toronto 2023 Lockbit ransomware gang claims […]

Citrix has urged customers of NetScaler ADC and NetScaler Gateway to install updated versions of the networking products to prevent active exploitation of vulnerabilities that could lead to information disclosure and DoS attacks. NetScaler ADC (Application Delivery Controller) and NetScaler Gateway were designed to enhance the performance, security, and availability of applications and services within […]

Citrix warned of attacks actively exploiting the vulnerability CVE-2023-4966 in NetScaler ADC and Gateway appliances. Citrix is urging administrators to secure all NetScaler ADC and Gateway appliances against the CVE-2023-4966 vulnerability, which is actively exploited in attacks. On October 10, Citrix published a security bulletin related to a critical vulnerability, tracked as CVE-2023-4966, in Citrix NetScaler ADC/Gateway devices. […]

For the latest discoveries in cyber research for the week of 23rd October, please download our Threat_Intelligence Bulletin. TOP ATTACKS AND BREACHES Attackers have gained access to parts of the network of the cloud identity authentication giant Okta. The hackers managed to gain access to the firm’s support unit for at least two weeks and […]

A new round of the weekly SecurityAffairs newsletter arrived! Every week the best security articles from Security Affairs are free for you in your email box. Enjoy a new round of the weekly SecurityAffairs newsletter, including the international press. A threat actor is selling access to Facebook and Instagram’s Police Portal Threat actors breached Okta […]

Here’s an overview of some of last week’s most interesting news, articles, interviews and videos: North Korean hackers are targeting software developers and impersonating IT workers State-sponsored North Korean hackers have significantly intensified their focus on the IT sector in recent years, by infiltrating firms developing software and companies lookind for IT workers. The collaborative power of CISOs, CTOs and CIOs for a secure future In this Help Net Security interview, Phil Venables, CISO at … More →

A recently patched Citrix NetScaler ADC/Gateway information disclosure vulnerability (CVE-2023-4966) has been exploited by attackers in the wild since late August 2023, Mandiant researchers have revealed. About CVE-2023-4966 Citrix’s security advisory, published on October 10, says that the vulnerability can lead to sensitive information disclosure, but did not explain what type of information can be disclosed to attackers. CVE-2023-4966 is exploitable remotely without authentication, and a successful attack does not hinge on user interaction. The … More →

Experts reported that the vulnerability CVE-2023-4966 in Citrix NetScaler ADC/Gateway devices has been exploited in attacks since late August. On October 10, Citrix published a security bulletin related to a critical vulnerability, tracked as CVE-2023-4966, in Citrix NetScaler ADC/Gateway devices. “Exploits of CVE-2023-4966 on unmitigated appliances have been observed.” reported Citrix. “Cloud Software Group strongly urges customers of […]

Mandiant says the recently patched Citrix NetScaler vulnerability CVE-2023-4966 had been exploited as zero-day since August.

Citrix has released patches for a critical information disclosure vulnerability in NetScaler ADC and NetScaler Gateway.