# CVE-2026-31883: FreeRDP has a `size_t` underflow in ADPCM decoder leads to heap-buffer-overflow write

> A size_t underflow in FreeRDP's ADPCM decoders causes a heap-buffer-overflow write, potentially allowing remote code execution or denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Mar 2026
- **Updated:** 16 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-31883, GHSA-85x9-4xxp-xhm5, MINI-3h55-g6h5-gh4j, UBUNTU-CVE-2026-31883

## What is CVE-2026-31883?

CVE-2026-31883 is a medium-severity vulnerability in Freerdp Freerdp, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.24.0, a size_t underflow in the IMA-ADPCM and MS-ADPCM audio decoders leads to heap-buffer-overflow write via the RDPSND audio channel. In libfreerdp/codec/dsp.c, the IMA-ADPCM and MS-ADPCM decoders subtract block header sizes from a size_t variable without checking for underflow. When nBlockAlign (received from the server) is set such that size % block_size == 0 triggers the header parsing at a point where size is smaller than the header (4 or 8 bytes), the subtraction wraps size to ~SIZE_MAX. The while (size > 0) loop then continues for an astronomical number of iterations. This vulnerability is fixed in 3.24.0.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound)), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-31883?

It affects 1 product.


Products: Freerdp Freerdp.

## How do I fix CVE-2026-31883?

Upgrade to a fixed version.

## Is CVE-2026-31883 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31883 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-2026-31883 and fix it if it is affected.

What it is: CVE-2026-31883 is a medium-severity vulnerability in Freerdp Freerdp, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31883 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-2026-31883/ (Markdown: https://insights.sbomify.com/CVE-2026-31883/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31883
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31883
- OSV: https://osv.dev/vulnerability/CVE-2026-31883

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31883/
Summaries are generated and may contain mistakes; the official description above is the record.