CVE-2023-6549
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
- CVSS
- 8.2Highscored by the publisher (CNA)
- Exploited in the wild
- Yes, in CISA KEV since 17 Jan 2024CISA deadline for US federal agencies: 7 Feb 2024
- EPSS
- 57.6%chance of exploitation in the next 30 daystop 1% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 17 Jan 2024analysed here 12 Nov 2026
Do first. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable. (CISA's required action for this KEV entry)
Summary
Triage
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Cloud Software Group NetScaler ADC | >= 14.1 and < 12.35>= 13.1 and < 51.15>= 13.0 and < 92.21>= 13.1-FIPS and < 37.176>= 12.1-FIPS and < 55.302>= 12.1-NDcPP and < 55.302Vendor says fixed in: not stated |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- citrix:netscaler_application_delivery_controller
- citrix:netscaler_gateway
Fix and mitigation
WAF and other mitigations
Can a WAF block it? No. This is a memory-corruption bug. Generic WAF rules do not recognise the input that triggers it; only a rule written for this specific CVE can, and only if the triggering request has a recognisable shape.
Also consider: patch
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 17 Jan 2024.
- CISA due date
- 7 Feb 2024, the remediation deadline for US federal agencies
- CISA required action
- Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Public exploit code
- Detection templates only, no public exploit found: 1 Nuclei template
- CISA SSVC
- exploitation active, automatable yes, technical impact partialAssessed by CISA 31 Jan 2024 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Nuclei
- Citrix Netscaler ADC & Gateway - Out-Of-Bounds Memory Readdetection template, critical
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 17 Jan 2024Added to CISA KEV (exploited in the wild)
- 17 Jan 2024Published1 day later
- 31 Jan 2024CISA SSVC assessment: exploitation active13 days later
- 7 Feb 2024CISA remediation due date (US federal agencies)7 days later
- 21 Oct 2025CVE record last updated623 days (about 2 years) later
- 12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
| Metric | Value | What it means |
|---|---|---|
| Attack vector | NetworkReachable over the internet or any routable network. | Reachable over the internet or any routable network. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | NoneThe attacker needs no prior access. | The attacker needs no prior access. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | NoneNo data disclosure. | No data disclosure. |
| Integrity | LowLimited modification possible. | Limited modification possible. |
| Availability | HighFull outage possible. | Full outage possible. |
Common questions
Is CVE-2023-6549 being exploited?
Yes. CVE-2023-6549 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2023-6549?
CVE-2023-6549 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2023-6549?
Yes. A fix has been recorded for CVE-2023-6549. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2023-6549 affect?
CVE-2023-6549 affects citrix:netscaler_application_delivery_controller, citrix:netscaler_gateway. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
2 references in the CVE record, grouped by the tags the record gives them.
Other links (2)
- support.citrix.com /article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-6549
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Nuclei templates: detection templates
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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