Threats / Citrix / CVE-2023-6549
CVE-2023-6549
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Citrix NetScaler ADC and Gateway vulnerability
Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability enabling denial-of-service attacks when configured as a Gateway or AAA virtual server.
Verdict
Today item — known-exploited.
A buffer overflow in Citrix NetScaler ADC and Gateway allows unauthenticated attackers to trigger denial-of-service conditions on affected deployments. The vulnerability is actively exploited in the wild.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
21 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-01-17).
Probability (EPSS)
EPSS 0.57633 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Citrix, NetScaler ADC and NetScaler Gateway. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-119 Memory Buffer Bounds Error — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious request targeting the buffer overflow in the Gateway or AAA virtual server component.
Business
Service availability is disrupted as the NetScaler instance crashes or becomes unresponsive.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I send the crafted payload to the exposed NetScaler endpoint without authentication.
Business
VPN access, ICA Proxy, CVPN, RDP Proxy, or AAA services become unavailable to legitimate users.
3
Lateral reach — past segmentation narrative 3
Attacker
I repeat or automate the attack to maintain denial-of-service conditions.
Business
Business operations dependent on remote access or authentication services experience extended downtime and revenue loss.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05