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Citrix released security updates for NetScaler ADC and NetScaler Gateway to fix multiple vulnerabilities, led by CVE-2025-5777, a critical out-of-bounds read flaw dubbed "Citrix Bleed 2" because of its similarity to the 2023 Citrix Bleed bug. The vulnerability affects NetScaler deployments used as a Gateway or virtual AAA server and can let a remote unauthenticated attacker read memory, steal sensitive data such as credentials and configuration, hijack sessions, bypass MFA, and potentially gain broader control of affected systems. Citrix and third-party reporting also highlighted CVE-2025-6543, a denial-of-service flaw reported as actively exploited, and CVE-2025-5349, a high-severity improper access control issue in the NetScaler Management Interface that could allow unauthorized access from the same network segment.
Security researchers reported signs consistent with real-world exploitation of CVE-2025-5777 for initial access, including hijacked Citrix web sessions reused across multiple IP addresses, LDAP-based Active Directory reconnaissance, and use of ADExplorer64.exe against multiple domain controllers. Citrix urged administrators to upgrade affected versions immediately, including NetScaler ADC and Gateway 14.1 before 14.1-43.56, 13.1 before 13.1-58.32, 13.1-FIPS/NDcPP before 13.1-37.235-FIPS/NDcPP, and 12.1-FIPS before 12.1-55.328-FIPS, while noting older 12.1 and 13.0 branches are end-of-life. The company also recommended terminating active ICA and PCoIP sessions after patching HA pairs or clusters and monitoring for anomalous HTTP activity associated with session theft.
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3 events from the most recent confirmed update back to the earliest known activity.
CSIRT.SK stated that CVE-2025-5777, also called Citrix Bleed 2, is actively exploited and can enable out-of-bounds memory reads, credential and configuration theft, MFA bypass, and possible full system compromise in affected NetScaler deployments. The notice also highlighted Citrix's patch for CVE-2025-5349 in the NetScaler Management Interface.
ReliaQuest reported indicators consistent with real-world exploitation of CVE-2025-5777 for initial access, despite no public reporting cited in the reference. Observed activity included hijacked Citrix web sessions, session reuse across multiple IPs, LDAP-based Active Directory reconnaissance, and use of ADExplorer64.exe across multiple domain controllers.
On 2025-06-17, Citrix issued an advisory and released updates for NetScaler ADC and Gateway vulnerabilities including CVE-2025-5777 and CVE-2025-6543. The guidance included upgrading to fixed versions and terminating active ICA/PCoIP sessions after patching.
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Attackers continued to target Citrix NetScaler ADC and NetScaler Gateway systems vulnerable to **`CVE-2025-5777`**, a critical flaw also dubbed **Citrix Bleed 2** that can let unauthenticated attackers obtain sensitive information and hijack user sessions. The vulnerability affects NetScaler deployments configured as described in Citrix’s security bulletin, and public advisories warned that exploitation could also enable arbitrary file reads, broader information disclosure, and denial of service on exposed appliances. SOC telemetry showed exploitation attempts persisted well beyond initial disclosure, with detections recorded from mid-July through September 2025 rather than a brief spike. One observed pattern used a `POST` request to `/p/u/doAuthentication.do` with an unusually long `User-Agent` header to retrieve memory data, while much of the attack traffic was traced to infrastructure in the United States and France. Citrix and national defenders urged organizations to identify affected NetScaler ADC and Gateway versions and apply the vendor’s fixed releases immediately.
Aug 15, 2026
Multiple severe vulnerabilities in **Citrix ADC** and **NetScaler Gateway** exposed organizations to unauthenticated compromise, including remote code execution in `CVE-2019-19781` and `CVE-2023-3519`, as well as memory disclosure in `CVE-2023-4966` (**CitrixBleed**) and the later `CVE-2025-5777` variant. Public reporting showed that `CVE-2019-19781` could be exploited through crafted HTTP requests that abused directory traversal and template parsing to execute commands on vulnerable appliances, while research on `CVE-2023-3519` examined another critical path to code execution on internet-facing Citrix infrastructure.
Jun 29, 2026
Citrix released fixes for six vulnerabilities in **NetScaler ADC** and **NetScaler Gateway**, including **CVE-2026-8451**, a high-severity out-of-bounds read flaw that can leak sensitive memory from appliances configured as a **SAML Identity Provider**. The bug affects customer-managed NetScaler ADC, Gateway, and related **FIPS/NDcPP** variants, and can expose memory contents in the `NSC_TASS` cookie via malformed requests to the `/saml/login` endpoint. Other patched issues include **CVE-2026-8452**, **CVE-2026-8655**, **CVE-2026-10816**, **CVE-2026-10817**, and **CVE-2026-13474**, covering risks such as arbitrary file reads, memory corruption, and denial of service, including a new **HTTP/2 Bomb** attack. Security researchers and defenders reported that **CVE-2026-8451** was exploited in the wild less than 24 hours after public disclosure, with Lupovis observing threat actors scanning exposed NetScaler systems and sending exploit payloads immediately after receiving valid `200 OK` responses. The observed activity matched public technical details released by watchTowr, using malformed SAML `AuthnRequest` data padded to trigger the overread condition. Government and industry advisories urged organizations to patch immediately, disable **SAML IdP** where patching is not possible, review `/saml/login` traffic and `NSC_TASS` cookie values for signs of compromise, restrict management exposure, and follow Citrix incident guidance if exploitation is suspected.
Jul 9, 2026