Citrix Bleed 2 — NetScaler ADC/Gateway memory-disclosure leaking session tokens

CVE-2025-5777 is a memory-disclosure flaw in Citrix NetScaler ADC and NetScaler Gateway. Same class as the original Citrix Bleed — NVD describes it as insufficient input validation leading to a memory overread when the NetScaler is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or as an AAA virtual server. Unauthenticated. Remote. The memory that leaks back to the caller holds live session tokens for already-authenticated users — replay one and you are inside as that user, MFA already fired for the legitimate session.

That is why it is called “Citrix Bleed 2.” Same primitive, same operational outcome, one CVE year after the original. If you patched, killed sessions, and rotated credentials the last time, do it again now.

Affected

NetScaler ADC and NetScaler Gateway builds fronting the internet as VPN / ICA Proxy / CVPN / RDP Proxy or AAA virtual server. Citrix’s security bulletin index carries the current advisory for CVE-2025-5777 with the fixed-build numbers per branch — check your appliance version against it directly, do not rely on secondhand version lists that go stale between Citrix bulletin revisions.

Exploitation status

On the CISA Known Exploited Vulnerabilities catalog. Federal civilian agencies were placed on notice under BOD 22-01. In parallel, ransomware affiliates aligned with the Anubis operation have been observed using CVE-2025-5777 as the initial-access vector against unpatched NetScaler estates — same technique showing up in more than one disclosed intrusion report through July 2026.

NVD scores it 7.5 / high, not critical. Two things about that number. First, it is what NVD published, so it is what this entry lists — severity follows the source, not the vendor’s marketing language or my gut. Second, the operational impact of the exploit chain — bypass of MFA on an internet-facing management surface — is nastier than the score reads on paper. Score the CVE by what the chain lets an attacker skip, not by the label.

What to actually do

• Patch to a fixed NetScaler build. Citrix’s advisory has the current fixed versions per branch; apply them everywhere the ADC or Gateway is internet-exposed. Do it this week.
• Kill active sessions after patching. Same instruction Citrix issued for Citrix Bleed 1: tokens siphoned before the patch remain replayable. Terminate ICA and PCoIP sessions post-patch — closing the leak does not invalidate what already leaked.
• Rotate credentials the appliance holds or brokers. SAML signing keys, LDAP bind creds, service accounts used for backend auth. Assume anything reachable from the box is compromised, and treat it that way.
• Get the management interface off the public internet. Same underlying problem behind every NetScaler CVE this cycle. Patching is the fix for this bug; not exposing the plane is the fix for the class.

Sources

• NVD: CVE-2025-5777
• CISA KEV: CVE-2025-5777 in the catalog
• Citrix security bulletins index: support.citrix.com/product/netscaler-adc/security-bulletins
• 0dayNews coverage: Anubis ransomware exploits Citrix Bleed 2