The vulnerability allows an attacker to predict the exact initial sequence number of a TCP connection because the device uses a deterministic algorithm based on prior sequence numbers. With this information, an adversary can forge packets or hijack an existing session, potentially sending malicious payloads that the system may accept. This flaw is identified as CWE-342 and can lead to TCP session hijacking.

Citrix NetScaler ADC is affected in all versions before 14.1‑73.37, before 13.1‑64.23, before 14.1‑73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP. Citrix NetScaler Gateway is affected in all versions before 14.1‑73.37 and before 13.1‑64.23. The vulnerability does not impact newer releases past the stated thresholds.

The CVSS score is 8.8, indicating a high severity. Though EPSS data is not available, the absence of a KEV listing suggests moderate in‑traffic but not yet exploited at scale. Attackers would need network access to the affected device and to hijack a TCP session. The deterministic nature of the ISN generation lowers the barrier to exploitation, making the risk significant for exposed appliances.