# CVE-2026-22858: FreeRDP has a global-buffer-overflow in crypto_base64_decode

> A global buffer overflow in FreeRDP's Base64 decoder allows attackers to cause out-of-bounds access, potentially leading to code execution or crashes.

- **Severity:** Medium 5.6 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 14 Jan 2026
- **Updated:** 19 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-22858, GHSA-qmqf-m84q-x896, MINI-rjw5-38f3-3hfr, UBUNTU-CVE-2026-22858

## What is CVE-2026-22858?

CVE-2026-22858 is a medium-severity memory corruption vulnerability in Freerdp Freerdp, published on 14 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.20.1, global-buffer-overflow was observed in FreeRDP's Base64 decoding path. The root cause appears to be implementation-defined char signedness: on Arm/AArch64 builds, plain char is treated as unsigned, so the guard c <= 0 can be optimized into a simple c != 0 check. As a result, non-ASCII bytes (e.g., 0x80-0xFF) may bypass the intended range restriction and be used as an index into a global lookup table, causing out-of-bounds access. This vulnerability is fixed in 3.20.1.

Weakness: CWE-787 (Out-of-bounds Write), CWE-758 (Reliance on Undefined, Unspecified, or Implementation-Defined Behavior), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-22858?

It affects 1 product.


Products: Freerdp Freerdp.

## How do I fix CVE-2026-22858?

Upgrade to a fixed version.

## Is CVE-2026-22858 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-22858 exists.

## 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-2026-22858 and fix it if it is affected.

What it is: CVE-2026-22858 is a medium-severity memory corruption vulnerability in Freerdp Freerdp, published on 14 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-22858 exists.

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-2026-22858/ (Markdown: https://insights.sbomify.com/CVE-2026-22858/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-22858
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-22858
- OSV: https://osv.dev/vulnerability/CVE-2026-22858

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-22858/
Summaries are generated and may contain mistakes; the official description above is the record.