# CVE-2025-6543: Citrix NetScaler ADC and Gateway Buffer Overflow

> Attackers can cause memory overflow leading to denial of service or unintended control flow in NetScaler Gateway or AAA virtual servers.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L`)
- **Exploited in the wild:** Yes, since 30 Jun 2025 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Jun 2025
- **Updated:** 26 Feb 2026
- **Also known as:** GHSA-9gqr-6728-fpv3

## What is CVE-2025-6543?

CVE-2025-6543 is a critical memory corruption vulnerability in NetScaler ADC, published on 25 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server

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

## Which versions are affected by CVE-2025-6543?

It affects 2 products.


Products: Citrix NetScaler ADC, Citrix Netscaler Gateway.

## How do I fix CVE-2025-6543?

No fix has been published for CVE-2025-6543 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 21 Jul 2025.

## Is CVE-2025-6543 being exploited?

Yes. Attackers have exploited CVE-2025-6543 in the wild since at least 30 Jun 2025.

Public exploit code:

- Multi-host, multi-port scanner and auditor for CVE-2025-6543-affected NetScaler devices. Supports SNMP and SSH enumeration with optional CSV reporting and exploit stubs. (github_poc): https://github.com/abrewer251/CVE-2025-6543_CitrixNetScaler_PoC
- Script para determinar si Citrix es vulnerable al CVE-2025-6543  (github_poc): https://github.com/grupooruss/Citrix-cve-2025-6543
- Citrix Bleed 2 PoC (github_poc): https://github.com/lex1010/CVE-2025-6543

## Other vulnerabilities in 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-2025-6543 and fix it if it is affected.

What it is: CVE-2025-6543 is a critical memory corruption vulnerability in NetScaler ADC, published on 25 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2025-6543 in the wild since at least 30 Jun 2025.

Affected product: 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-2025-6543/ (Markdown: https://insights.sbomify.com/CVE-2025-6543/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-6543
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-6543
- OSV: https://osv.dev/vulnerability/CVE-2025-6543

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-6543/
Summaries are generated and may contain mistakes; the official description above is the record.