CVE-2023-6549
HIGHCVE-2023-6549 is a high-severity (CVSS 8.2) Buffer Overflow vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2024-01-17) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
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
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2024-01-17. Federal agencies were required to remediate by 2024-02-07.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2023-6549.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2023-6549 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 396,966 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
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
Affected Products
netscaler application delivery controllercitrixnetscaler gatewaycitrixResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2023-6549 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
How to detect CVE-2023-6549
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2023-6549 -u https://target- Template
- Citrix Netscaler ADC & Gateway - Out-Of-Bounds Memory Read
- Severity
- critical
- Impact
- The vulnerability allows an attacker to recover potentially sensitive data from memory. Although in most cases nothing of value is returned, we have observed instances where POST request bodies are leaked.
- Remediation
- Update to version 13.1-51.15 or later
Template by ProjectDiscovery nuclei-templates (ice3man), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2023-6549 in your dependencies?
Find it across , including transitive dependencies.