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Full vulnerability report · 2026
CVE-2026-8655High confidence

Multiple Memory overflow vulnerabilities leading to unpredictable or erroneous behavior and Denial of Service

NetScaler · ADC

8.8HighCVSS 4.0
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Fix not verified
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-40308

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Fix not verified
01

What, why and how

Multiple Memory overflow vulnerabilities in NetScaler ADC and NetScaler Gateway leading to unpredictable or erroneous behavior and Denial of Service if NetScaler ADC is configured as an LB of type Oracle OR NetScaler ADC is configured as a DNS Proxy OR NetScaler ADC is configured as a DNS recursive resolver deployment

What

Multiple Memory overflow vulnerabilities in NetScaler ADC and NetScaler Gateway leading to unpredictable or erroneous behavior and Denial of Service if NetScaler ADC is configured as an LB of type Oracle OR NetScaler ADC is configured as a DNS Proxy OR NetScaler ADC is configured as a DNS recursive resolver deployment

Why

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

Multiple Memory overflow vulnerabilities in NetScaler ADC and NetScaler Gateway leading to unpredictable or erroneous behavior and Denial of Service if NetScaler ADC is configured as an LB of type Oracle OR NetScaler ADC is configured as a DNS Proxy OR NetScaler ADC is configured as a DNS recursive resolver deployment

Why

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Improper Restriction of Operations within the Bounds of a Memory Buffer → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-119

CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:L

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCLowVulnerable-system confidentiality: A successful attack can cause a limited loss.VILowVulnerable-system integrity: A successful attack can cause a limited loss.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SALowSubsequent-system availability: A successful attack can cause a limited loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-119
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-2147Citrix Systems NetScaler ADC und Gateway: Mehrere Schwachstellen

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Citrix Systems NetScaler ADC und Gateway ausnutzen, um Informationen offenzulegen, einen Denial-of-Service-Zustand zu verursachen oder andere, nicht näher spezifizierte Auswirkungen auszulösen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0822Multiples vulnérabilités dans les produits Citrix

De multiples vulnérabilités ont été découvertes dans les produits Citrix. Certaines d'entre elles permettent à un attaquant de provoquer un déni de service à distance, une atteinte à la confidentialité des données et un problème de sécurité non spécifié par l'éditeur.

Official advisory ↗
CSIRT Italia · Italian · vulnerabilita-in-prodotti-citrix-10Vulnerabilità in prodotti Citrix

Nel dettaglio, la vulnerabilità identificata tramite la CVE-2026-8451 , di tipo " Out-of-bounds Read " e con score CVSS 4.0 pari a 8.8, è dovuta da una non adeguata validazione dell'input utente durante l'elaborazione delle richieste SAML, che può determinare una condizione di lettura oltre i limiti della memoria allocata. Tale vulnerabilità, qualora sfruttata, potrebbe consentire ad un utente malintenzionato l'accesso ad informazioni sensibili sui sistemi interessati. È stato rilevato lo sfruttamento attivo in rete della seconda vulnerabilità, identificata tramite la CVE-2026-8452 , di tipo "Improper Restriction of Operations" e con score CVSS 4.0 pari a 8.8; la problematica è dovuta all’utilizzo di meccanismi non adeguati durante la validazione delle dimensioni dei dati elaborati nella gestione delle richieste SAML, che può determinare una condizione di heap-based buffer overflow . Nel dettaglio, dati opportunamente predisposti contenuti nell'elemento SignedInfo di messaggi SAML possono eccedere le dimensioni di un buffer allocato in memoria e corrompere eventuali strutture dati nelle locazioni di memoria adiacenti, consentendo la manipolazione del flusso di esecuzione del processo interessato. Tale vulnerabilità, qualora sfruttata mediante richieste opportunamente predisposte, potrebbe consentire ad un utente malintenzionato remoto e non autenticato di compromettere la disponibilità del servizio e, come dimostrato da Proof of Concept (PoC) pubblici, di eseguire codice arbitrario sui sistemi interessati.

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0216Kwetsbaarheden verholpen in Citrix Netscaler ADC en Netscaler Gateway

De kwetsbaarheden met de kenmerken CVE-2026-8451 en CVE-2026-10817 ontstaan door onvoldoende invoervalidatie, waarbij de software invoergroottes en -grenzen niet correct controleert. Dit kan leiden tot geheugenoverlezingen, wat kan resulteren in ongeautoriseerde openbaarmaking van gevoelige informatie, wanneer de producten zijn geconfigureerd als SAML IDP, of als TCP TimeStamp is ingeschakeld bij een TCP-profiel dat is gekoppeld aan een virtuele server van het type: Load Balancing (LB), Content Switching (CS) of VPN. De kwetsbaarheden met de kenmerken CVE-2026-8452 en CVE-2026-8655 bevinden zich in de manier waarop geheugen wordt beheerd in NetScaler ADC en NetScaler Gateway. Dit kan leiden tot een denial-of-service (DoS) of een ongewenste control flow wanneer de producten zijn geconfigureerd als Gateway, DNS-proxy, recursieve DNS-resolver of AAA-virtuele server. De kwetsbaarheid met het kenmerk CVE-2026-13474 ontstaat door het onjuist vrijgeven van geheugen. Kwaadwillenden kunnen deze kwetsbaarheid misbruiken door via speciaal geprepareerde HTTP/2-verzoeken een denial-of-service (DoS) te veroorzaken. De kwetsbaarheid met het kenmerk CVE-2026-10816 betreft een probleem met de toegangscontrole binnen de Management Interface. Niet-geauthenticeerde kwaadwillenden op afstand kunnen de kwetsbaarheid misbruiken om willekeurige bestanden uit te lezen. Dit kan resulteren in ongeautoriseerde openbaarmaking van gevoelige informatie. Onderzoekers hebben Proof-of-Concept (PoC) code gedeeld waarmee de kwetsbaarheid met kenmerk CVE-2026-8451 kan worden aangetoond. **UPDATE:** Inmiddels hebben dezelfde onderzoekers ook Proof-of-Concept (PoC) code gepubliceerd waarmee uitvoer van willekeurige code mogelijk wordt. Het kwetsbare systeem moet hiervoor wel zijn geconfigureerd om middels SAML ingezet te zijn als Identity Provider. Dit is geen gebruikelijke configuratie, omdat best practices adviseren het Identity Management en Access Management gescheiden te houden.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
  • ADC: 14.1 < 72.61, 13.1 < 63.18, 14.1 FIPS < 72.61, 13.1 FIPS and NDcPP < 37.272
  • Gateway: 14.1 < 72.61, 13.1 < 63.18
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 30 Jun 2026 · Last source change 30 Jun 2026, 13:33 UTC · CWE-119 · Improper Restriction of Operations within the Bounds of a Memory Buffer

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-40308
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCISA ADP
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-8655 · cve.blacktree.nl