Citrix · Memory corruption
Citrix NetScaler Out-of-Bounds Read Vulnerability
At a glance
Actively exploited in the wild — prioritise confirming exposure.
High rather than Critical: exposure is scored at a default because we cannot see your systems or suppliers. If you run or depend on Citrix, treat it as Critical.
Briefing
- Do not treat uncorroborated claims as confirmed breaches.
Questions to ask IT
- Do we run Citrix, and which versions?
- Is any of it reachable from the internet?
- Have we checked whether it has already been used against us?
- If it is still not patched, what mitigation is in place, and what is holding the fix up?
Next steps
- Confirm exposure, mitigation status and any service interruption risk.
Vulnerability facts
Full CVE detail CVE-2026-3055- 9.3 · CriticalExploitable over the network without any account, and no one has to click or open anything. High impact on confidentiality, integrity and availability; low on subsequent confidentiality, subsequent integrity and subsequent availability.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- Listed: attacks using it have been seen (on the catalogue since )
- Elevated attack likelihood (~91.5% in 30 days)
No technical write-up beyond these facts and the summary below yet.
Next steps
- Confirm whether affected products/versions are present and prioritise patching or mitigations
Summary
- Citrix NetScaler ADC (formerly Citrix ADC), NetScaler Gateway (formerly Citrix Gateway) and NetScaler ADC FIPS and NDcPP contain an out-of-bounds reads vulnerability when configured as a SAML IDP leading to memory overread.
- CVE-2026-3055 is listed in known-exploited catalogue (exploitation in the wild)
- Authoritative catalogues report active exploitation of this vulnerability.
Why this matters in the UK
- Known-exploited catalogue reports exploitation in the wild
Products and services involved
- Citrix90% match confidence · CVE-2026-3055
Pulse
Last checked 4d ago · Recheck overdue since 5 Nov 2026, 21:33 UK time · 2 quiet checks collapsed
in the next 30 days first recorded at 87.2% (elevated likelihood signal, not confirmed exploitation).
Elevated — confirm exposure; this is a probability signal, not confirmed exploitation.
3 quiet checks hidden.
Sources
Citrix NetScaler Out-of-Bounds Read Vulnerability
How we know
Statements extracted from sources. Higher confidence means stronger corroboration.
- ConfirmedHeadline90% confidence
Citrix NetScaler Out-of-Bounds Read Vulnerability
- ConfirmedSummary fact75% confidence
Citrix NetScaler ADC (formerly Citrix ADC), NetScaler Gateway (formerly Citrix Gateway) and NetScaler ADC FIPS and NDcPP contain an out-of-bounds reads vulnerability when configured as a SAML IDP leading to memory overread. Affects Citrix NetScaler. Known ransomware campaign use: Unknown. Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- ConfirmedCVE identifier95% confidence
Event involves CVE-2026-3055
- ConfirmedKnown-exploited catalogue98% confidence
CVE-2026-3055 is listed in known-exploited catalogue (exploitation in the wild)