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NVD / CVE Program· CNA Citrix

CVE-2023-6549: Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial…

HighCVSS 7.5 · v3.1KEVWeaponized Fix available

Noroxi assessment

Priority: This week (action score 77/100)

  • CISA has confirmed exploitation in the wild (Jan 17, 2024). Remediation deadline for US federal agencies: Feb 7, 2024.
  • A ready-made attack module is public (Nuclei); exploiting it takes no special expertise.
  • Probability of exploitation in the next 30 days: 57.6% (FIRST EPSS); higher than 99% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Cloud Software Group NetScaler ADC 12.35, 37.176, 51.15.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Don’t wait for the next maintenance window. Upgrade to Cloud Software Group NetScaler ADC 12.35, 37.176, 51.15 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read

Published
Jan 17, 2024
Updated
Jun 17, 2026
EPSS
57.6% · 99th percentile

Report tools

JSON

Action score

77

This week

Don’t wait for the next maintenance window.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
30 / 30 · Listed
EPSS
17 / 30 · 57.6%

CISA SSVC decision

Exploitation
active
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
7.5
CNA · Citrix
8.2
0.7 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Jan 17, 2024. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Feb 7, 2024.

Get told when this record changes

  • In CISA KEV: exploitation in the wild confirmed
  • Weaponized exploit exists
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2023-6549

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
citrixnetscaler application delivery controller
citrixnetscaler gateway

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Citrix). Independent of NVD's CPE analysis and usually ahead of it.

  • Cloud Software Group NetScaler ADC

    • 14.1 and later · before 12.35affected · patch
    • 13.1 and later · before 51.15affected · patch
    • 13.0 and later · before 92.21affected · patch
    • 13.1-FIPS and later · before 37.176affected · patch
    • 12.1-FIPS and later · before 55.302affected · patch
    • 12.1-NDcPP and later · before 55.302affected · patch

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • citrix netscaler gateway13.0 and later · before 13.0-92.21
  • citrix netscaler gateway13.1 and later · before 13.1-51.15
  • citrix netscaler gateway14.1 and later · before 14.1-12.35

Same product

citrix: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-3519Unauthenticated remote code executionKEV
    99Now
  • CVE-2025-5777NetScaler ADC and NetScaler Gateway - Insufficient input validation leading to memory overreadKEV
    97Now
  • CVE-2026-3055Insufficient input validation leading to memory overreadKEV
    94Now

Published before and after this one in the same product

  • ← EarlierCVE-2023-4967Oct 27, 2023 · Denial of Service in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or…
    30Monitor
  • ← EarlierCVE-2023-6548Jan 17, 2024 · Improper Control of Generation of Code ('Code Injection') in NetScaler ADC and NetScaler Gateway allows an attacker with access to NSIP…KEV
    66This week
  • Later →CVE-2024-5491Jul 10, 2024 · Denial of Service in NetScaler ADC and NetScaler Gateway in NetScaler
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Cloud Software Group NetScaler ADC12.35Vendor (CNA)
Cloud Software Group NetScaler ADC37.176Vendor (CNA)
Cloud Software Group NetScaler ADC51.15Vendor (CNA)
Cloud Software Group NetScaler ADC55.302Vendor (CNA)
Cloud Software Group NetScaler ADC92.21Vendor (CNA)

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Nuclei detection template ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Nuclei detection templateNuclei template CVE-2023-6549 —

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. CISA KEV-1 d
  2. Published
  3. TodayNov 13, 2026+1031 d

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2023-496699 days apartUnauthenticated sensitive information disclosureKEV
    90Now
  • CVE-2025-6543525 days apartMemory overflow vulnerability leading to unintended control flow and Denial of ServiceKEV
    69This week
  • CVE-2024-8534300 days apartMemory safety vulnerability leading to memory corruption and Denial of Service
    33Monitor
  • CVE-2023-496782 days apartDenial of Service in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or…
    30Monitor

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-119 · Improper Restriction of Operations within the Bounds of a Memory Buffer

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records