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Researchers detailed how ransomware operators linked to LockBit exploited Citrix NetScaler ADC and Gateway appliances through the original CitrixBleed flaw, CVE-2023-4966, using stolen session data to support follow-on access and affiliate infrastructure operations. An OSINT analysis built from joint government and Boeing-published indicators identified additional suspected LockBit infrastructure spanning command-and-control, remote management, FTP, RDP, and OpenVPN services, with recurring hosting patterns and overlaps with tooling and infrastructure previously associated with Akira, Avaddon, Cerber, BumbleBee, Raccoon Stealer, RecordBreaker, SolarMarker, 8Base, and ShadowSyndicate.
A later root-cause analysis of CitrixBleed 2, CVE-2025-5777, showed that a malformed POST request to /p/u/doAuthentication.do can trigger an out-of-bounds memory disclosure on vulnerable NetScaler devices, leaking up to 0x7F bytes per request in an authentication failure response. Researchers warned that exposed memory may include credentials, session cookies, and private keys, making the bug a low-noise path to unauthenticated access similar in impact to the earlier CitrixBleed incidents; Citrix issued fixes and defenders were urged to patch immediately, invalidate sessions, reset credentials, rotate certificates and secrets where needed, and review telemetry for LockBit-related indicators, while broad community IOC feeds for suspected LockBit 5.0 activity have also circulated with explicit false-positive caveats.
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5 events from the most recent confirmed update back to the earliest known activity.
The Medium post for the LockBit 5.0 detection content was published on December 9, 2025, reflecting the release window for the experimental Sigma IOC feed. It documented broad detection logic for domains, IPs, hashes, URL patterns, hostnames, and command-line behaviors tied to suspected LockBit 5.0 activity.
Onur OKTAY published an experimental Sigma rule and IOC feed for suspected LockBit 5.0 activity, aggregating known and inferred indicators across network and endpoint telemetry. The feed explicitly warned that several indicators were inferential and carried high false-positive risk.
Knownsec 404 Team published a technical root cause analysis of CVE-2025-5777, explaining the malformed POST parsing bug in /p/u/doAuthentication.do and how it can leak memory in authentication failure responses. The article also noted that public proof-of-concept code already supported exploitation and urged immediate defensive action.
Citrix released fixes for CVE-2025-5777, a high-severity memory disclosure vulnerability affecting NetScaler ADC and Gateway. The flaw, later dubbed CitrixBleed 2, could expose sensitive memory contents to unauthenticated attackers.
OSINT Team published an infrastructure analysis linking LockBit 3.0 affiliates exploiting CVE-2023-4966 to additional command-and-control, remote management, FTP, RDP, and OpenVPN infrastructure. The research expanded on advisory and Boeing-linked indicators and identified overlaps with other ransomware and malware ecosystems.
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Citrix disclosed **CVE-2025-5777** in NetScaler ADC and NetScaler Gateway alongside **CVE-2025-5349**, warning that affected appliances could be exposed to remote exploitation. Public tracking by ENISA’s EUVD and subsequent reporting identified `CVE-2025-5777` as **CitrixBleed 2**, linking the issue to session exposure risks on internet-facing NetScaler deployments and raising concern for organizations that rely on the products for remote access. After the advisory, proof-of-concept and scanning tools for `CVE-2025-5777` appeared on GitHub, including repositories explicitly branded as **CitrixBleed 2** scanners. The rapid publication of exploit-related code lowered the barrier for attackers to identify vulnerable devices, increasing urgency for defenders to patch NetScaler systems, review exposed gateways, and monitor for signs of session theft or unauthorized access.
Jul 3, 2026
Attackers exploited **CitrixBleed 2** (`CVE-2025-5777`) in Citrix NetScaler ADC and Gateway appliances to steal session data from memory and hijack valid user sessions, enabling repeated compromises across multiple organizations. Huntress reported that the flaw, a pre-authentication memory over-read, was used as the likely initial access vector in a series of intrusions, allowing attackers to bypass the practical protections of MFA once a legitimate session token had been captured. After gaining access, the intruders followed a consistent post-compromise playbook on Windows systems: escalating privileges with a portable local privilege escalation tool abusing `REG_LINK` and `AppMgmt`, creating fake administrator accounts, and deploying remote access software including **ScreenConnect** and **Zoho Assist**. In at least one case, the activity culminated in **DragonForce ransomware**, and Huntress assessed the campaign was more likely tied to a successful initial access broker than a single ransomware operator, while urging defenders to patch vulnerable NetScaler systems, terminate active sessions, preserve logs, and hunt for suspicious accounts, hostnames, and tooling.
Jul 15, 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