# CVE-2023-6549: Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow

> Unauthenticated attackers can cause denial of service and read out-of-bounds memory in NetScaler ADC and Gateway.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Yes, since 17 Jan 2024 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Jan 2024
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-8fxh-p33g-qf5m

## What is CVE-2023-6549?

CVE-2023-6549 is a high-severity memory corruption vulnerability in Cloud Software Group NetScaler ADC, published on 17 Jan 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2023-6549?

It affects 2 products.


Products: Citrix NetScaler ADC, Citrix Netscaler Gateway.

## How do I fix CVE-2023-6549?

No fix has been published for CVE-2023-6549 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 7 Feb 2024.

## Is CVE-2023-6549 being exploited?

Yes. Attackers have exploited CVE-2023-6549 in the wild since at least 17 Jan 2024.

Public exploit code:

- Citrix Netscaler ADC & Gateway - Out-Of-Bounds Memory Read (nuclei): http/cves/2023/CVE-2023-6549.yaml

## Other vulnerabilities in Cloud Software Group NetScaler ADC

- [CVE-2023-3519](https://insights.sbomify.com/CVE-2023-3519/): Citrix NetScaler ADC and NetScaler Gateway Code Injection (critical 9.8, exploited in the wild)
- [CVE-2026-88771](https://insights.sbomify.com/CVE-2026-88771/): Citrix NetScaler Improper Input Validation (critical 9.5, exploited in the wild)
- [CVE-2026-88772](https://insights.sbomify.com/CVE-2026-88772/): Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer (critical 9.5, exploited in the wild)
- [CVE-2023-4966](https://insights.sbomify.com/CVE-2023-4966/): Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow (critical 9.4, exploited in the wild)
- [CVE-2026-19490](https://insights.sbomify.com/CVE-2026-19490/): Citrix NetScaler Authentication Bypass Using an Alternate Path or Channel (critical 9.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6549 and fix it if it is affected.

What it is: CVE-2023-6549 is a high-severity memory corruption vulnerability in Cloud Software Group NetScaler ADC, published on 17 Jan 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2023-6549 in the wild since at least 17 Jan 2024.

Affected product: Cloud Software Group NetScaler ADC. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-6549/ (Markdown: https://insights.sbomify.com/CVE-2023-6549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6549
- OSV: https://osv.dev/vulnerability/CVE-2023-6549

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From sbomify Insights: https://insights.sbomify.com/CVE-2023-6549/
Summaries are generated and may contain mistakes; the official description above is the record.