# CVE-2026-64620: FreeRDP before 3.28.0 Heap Buffer Overflow via crypto_rsa_common

> An unauthenticated attacker can cause a heap buffer overflow in FreeRDP servers using Standard Security, leading to denial of service.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Jul 2026
- **Updated:** 21 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-64620, GHSA-pjqx-v446-x7fc, GHSA-xmhx-cqxp-qrgq, MINI-c997-q4fh-pxw9, UBUNTU-CVE-2026-64620

## What is CVE-2026-64620?

CVE-2026-64620 is a critical memory corruption vulnerability in Freerdp Freerdp, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

FreeRDP before 3.28.0 (affected <=3.27.1) contains a heap-based buffer overflow in crypto_rsa_common() (libfreerdp/crypto/crypto.c). The function writes the modular-exponentiation result into the caller's output buffer via BN_bn2bin() and only afterward checks output_length > out_length, so out-of-bounds bytes are written before the bounds check. On the server side, when a client selects RDP Standard Security, the encrypted client random is decrypted into a fixed 32-byte buffer. Because the server publishes its RSA public key, an unauthenticated attacker can forge a ciphertext whose decrypted value is up to the full modulus length (e.g. 256 bytes for RSA-2048), overflowing the 32-byte heap buffer by up to ~224 attacker-controlled bytes pre-authentication, resulting in denial of service.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-64620?

It affects 1 product.


Products: Freerdp Freerdp.

## How do I fix CVE-2026-64620?

Upgrade to a fixed version.

## Is CVE-2026-64620 being exploited?

There is no known exploitation of CVE-2026-64620 in the wild and no public exploit code.

## Other vulnerabilities in Freerdp Freerdp

- [CVE-2021-37594](https://insights.sbomify.com/CVE-2021-37594/): Other in n/a (critical 9.8)
- [CVE-2021-37595](https://insights.sbomify.com/CVE-2021-37595/): Other in n/a (critical 9.8)
- [CVE-2026-67305](https://insights.sbomify.com/CVE-2026-67305/): FreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr (critical 9.4)
- [CVE-2026-66402](https://insights.sbomify.com/CVE-2026-66402/): FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass (critical 9.3)
- [CVE-2026-67289](https://insights.sbomify.com/CVE-2026-67289/): FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64620 and fix it if it is affected.

What it is: CVE-2026-64620 is a critical memory corruption vulnerability in Freerdp Freerdp, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64620 in the wild and no public exploit code.

Affected product: Freerdp Freerdp. 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-2026-64620/ (Markdown: https://insights.sbomify.com/CVE-2026-64620/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64620
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64620
- OSV: https://osv.dev/vulnerability/CVE-2026-64620

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64620/
Summaries are generated and may contain mistakes; the official description above is the record.