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CVE-2026-19490 is an authentication-bypass vulnerability in SAML handling in customer-managed Citrix NetScaler ADC and NetScaler Gateway. An unauthenticated attacker can submit a crafted RelayState value that reaches nFactor authentication-context deserialization. On vulnerable builds, failed context verification propagates the attacker-controlled decoded RelayState length as an internal disposition code, selecting unintended processing branches. Depending on the input and virtual-server configuration, this can create an anonymous session or crash the packet engine. Gateway deployments with permissive global authorization can additionally expose an internal HTTP(S) proxy. Active exploitation is established, and CISA added the vulnerability to its Known Exploited Vulnerabilities catalog on September 9, 2026.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This is a standalone Python proof-of-concept repository for the claimed CVE-2026-19490 NetScaler ADC/Gateway SAML authentication bypass; it is not a Metasploit, Nuclei, or similar framework module. Its principal entry point, poc.py (about 37 KB), builds an unsigned SAML Response/Assertion, raw-DEFLATE compresses and Base64 encodes it, and supplies it to the HTTP-Redirect handler as GET /cgi/samlauth?SAMLResponse=... . The exploit claims that affected versions parse this redirect-binding input with strict processing disabled and misinterpret the default rejectUnsignedAssertion ON configuration as acceptance. It performs post-exploitation conservatively by checking for real NetScaler AAA cookies and making one session-validation request. It also supports endpoint-only checking, a safe oracle based on deliberately invalid issuer values and returned SAML errors, and --mint logic that follows the target's pre-auth SAML redirect to obtain assertion values needed for a viable forged response. The README documents required target configuration, affected/fixed builds, expected cookies, detection guidance, and mitigation via upgrade or STRICT mode. Lab tooling provisions a vulnerable NetScaler CPX 14.1-73.30 Docker instance, creates throwaway certificates and a SAML action/vServer, and records a demonstration. CPX is explicitly documented as unable to complete AAA session issuance because of licensing. demo/run-demo.sh and demo/demo.cast demonstrate version/configuration checks and the endpoint probe; lab/record-demo.sh records a licensed-VPX full-chain demonstration. tools/rec.py and tools/render.py are auxiliary asciinema recording/rendering utilities, not exploit logic. No destructive behavior, persistence, command execution, or external C2 infrastructure is present.
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An earlier authentication bypass vulnerability affecting Citrix NetScaler appliances, fixed in August 2026 by builds 14.1-73.32 and 13.1-63.21. It is mentioned as background to emphasize that those fixes do not protect against the two newly disclosed remote code execution vulnerabilities.
A previously disclosed NetScaler vulnerability mentioned only to clarify that it is unrelated to the two actively exploited zero-days discussed in the article.
An exploited authentication-bypass vulnerability in NetScaler products, mentioned only as background concerning prior August fixes.
A Citrix NetScaler vulnerability mentioned only as another recently added entry in CISA's Known Exploited Vulnerabilities catalog; no technical details are provided.
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