Amazon pins Cisco, Citrix zero
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2025-20337 | Unauthenticated Injection Flaw Allows Root RCE in Cisco ISE and ISE-PIC CVE-2025-20337 is a critical (CVSS 3.1: 10.0) injection vulnerability (CWE-74) in a specific API of Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC), caused by insufficient validation of user-supplied input. An unauthenticated, remote attacker can trigger it by submitting a crafted request to the affected API, with no valid credentials required. Successful exploitation allows arbitrary code execution on the underlying operating system with root privileges, giving the attacker full control of the affected device, consistent with the changed-scope, high-impact CVSS score. Any organization running Cisco ISE or ISE-PIC is potentially affected; CISA added the flaw to the Known Exploited Vulnerabilities catalog on 2025-07-28, and press reports indicate active exploitation, including zero-day use per Amazon threat intelligence coverage. EPSS assigns a 67% probability of exploitation within 30 days (99th percentile), and no public proof-of-concept is known. Do: Upgrade Cisco ISE and ISE-PIC to the fixed releases identified in Cisco's security advisory (fixed version details are not included in this data set), and check management/API logs for unauthenticated crafted API requests indicating exploitation. As an interim mitigation, restrict network access to the affected API and the ISE administration interface. Organizations covered by BOD 22-01 must apply vendor mitigations per Cisco's instructions or discontinue use of the product by the KEV remediation deadline. | 10.0 | 68% | KEV |
| moderatelikely on the order of tens of thousands of enterprise deployments worldwide (deployment-pattern estimate; no public install or scan counts) | |
| CVE-2025-5777 | Out-of-Bounds Read (Memory Overread) in Citrix NetScaler ADC and Gateway Citrix NetScaler ADC and NetScaler Gateway contain an out-of-bounds read (CWE-125) caused by insufficient input validation, which can cause the appliance to read beyond the intended memory buffer (a memory overread). The flaw is only triggerable when the appliance is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, or RDP Proxy) or as an AAA virtual server, so attackers who can reach those services can potentially induce the overread and obtain sensitive memory contents. Such disclosure could aid follow-on compromise, for example by exposing session or authentication data, and CISA notes known ransomware use. Organizations running NetScaler ADC or NetScaler Gateway in the affected Gateway/AAA configurations are exposed. The vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2025-07-10 with known ransomware use and an EPSS of 100% (100th percentile), indicating active exploitation, while no public PoC is known and a CVSS score has not yet been assigned. Do: Apply the fixed NetScaler ADC/Gateway builds per Citrix's security advisory (exact affected/fixed version ranges are not in the available data, so consult the bulletin); per CISA KEV, apply vendor mitigations, follow BOD 22-01 guidance for cloud services, or discontinue use if mitigations are unavailable. Inventory appliances for Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server configurations, since unconfigured/other deployments are not triggerable. After patching, terminate active and idle VPN sessions and hunt for anomalous access, given the known ransomware exploitation and the information-disclosure nature of the flaw. | 9.3 | 100% | KEV ransomware |
| massplausibly hundreds of thousands of installed/internet-exposed NetScaler ADC and Gateway appliances (public scans have historically shown on the order of… |
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The vendors disclosed and patched the defects last summer, but not before advanced attackers exploited the vulnerabilities to likely gain prolonged access for espionage, according to Amazon.
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Amazon’s threat intelligence team said it observed an advanced persistent threat group exploiting zero-day vulnerabilities affecting Cisco Identity Service Engine and Citrix NetScaler products before the vendors disclosed and patched the defects last summer.
Amazon’s MadPot honeypot service detected active exploitation of the critical defects — CVE-2025-5777 in Citrix and CVE-2025-20337 in Cisco — and through further investigation determined a highly resourced threat actor was behind the attacks, CJ Moses, chief information security officer of Amazon Integrated Security, said in a blog post Wednesday.
“We assess with high confidence it was the same threat actor observed exploiting both vulnerabilities,” Moses told CyberScoop in an email.
Amazon said its discovery reinforced multiple trends afoot, including threat groups’ increased focus on identity and network edge infrastructure and their ability to quickly weaponize vulnerabilities as zero-days before vendors disclose or patch defects in their products.
The origins and identity of the threat group behind the attacks remains unknown, yet Moses said “prolonged access to the target for espionage is the most likely objective.”
Amazon threat researchers said the threat group used custom malware with a backdoor specifically designed for Cisco ISE environments that demonstrated advanced evasion techniques. “The threat actor’s custom tooling demonstrated a deep understanding of enterprise Java applications, Tomcat internals and the specific architectural nuances of the Cisco ISE,” Moses said in the blog post.
Cisco disclosed CVE-2025-20337 on June 25, yet Amazon said exploitation was already underway in May. Amazon discovered the pre-disclosure exploits in early July and traced attacks back to May and June, Moses said.
Amazon disclosed active exploitation of the defect to Cisco, which informed its customers of the issue within hours, Moses added. He did not share information about how many organizations have been impacted by CVE-2025-20337 exploits.
Citrix disclosed CVE-2025-5777, also known as CitrixBleed 2 due to striking similarities with a 2023 defect in the same products, on June 17. The Cybersecurity and Infrastructure Security Agency added the exploit to its known exploited vulnerabilities catalog on July 10.
By mid-July, researchers had observed more than 11.5 million attack attempts, targeting thousands of sites since the exploit was disclosed.
Amazon declined to explain why it’s sharing information about active zero-day exploitation of the Cisco and Citrix defects months later, and the company said it doesn’t have additional information about more recent attacks linked to the vulnerabilities.
Moses noted the threat group’s use of multiple zero-day exploits indicates the attackers have advanced vulnerability research capabilities or access to undisclosed vulnerability information.
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