# CVE-2020-8940: Unchecked buffer overrun in enc_untrusted_recvmsg

> An attacker can read arbitrary memory, including secure enclave data, via an unchecked buffer overrun in Asylo's recvmsg implementation.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Dec 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-8gq9-69qw-7cch

## What is CVE-2020-8940?

CVE-2020-8940 is a medium-severity memory corruption vulnerability in Google LLC Asylo, published on 15 Dec 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An arbitrary memory read vulnerability in Asylo versions up to 0.6.0 allows an untrusted attacker to make a call to enc_untrusted_recvmsg using an attacker controlled result parameter. The parameter size is unchecked allowing the attacker to read memory locations outside of the intended buffer size including memory addresses within the secure enclave. We recommend upgrading or past commit fa6485c5d16a7355eab047d4a44345a73bc9131e

Weakness: CWE-125 (Out-of-bounds Read), CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2020-8940?

It affects 1 product.


Products: Google Asylo.

## How do I fix CVE-2020-8940?

No fix has been published for CVE-2020-8940 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-8940 being exploited?

There is no known exploitation of CVE-2020-8940 in the wild and no public exploit code.

## Other vulnerabilities in Google LLC Asylo

- [CVE-2021-22548](https://insights.sbomify.com/CVE-2021-22548/): Arbitrary enclave memory overread vulnerability in Asylo TrustedPrimitives::UntrustedCall (medium 6.5)
- [CVE-2021-22549](https://insights.sbomify.com/CVE-2021-22549/): Arbitrary enclave memory overwrite vulnerability in Asylo TrustedPrimitives::UntrustedCall (medium 6.5)
- [CVE-2021-22550](https://insights.sbomify.com/CVE-2021-22550/): Enclave memory overwrite/overread vulnerability in Asylo UntrustedCacheMalloc::GetBuffer (medium 6.5)
- [CVE-2020-8904](https://insights.sbomify.com/CVE-2020-8904/): Arbitrary trusted memory overwrite vulnerability in Asylo (medium 6.4)
- [CVE-2021-22552](https://insights.sbomify.com/CVE-2021-22552/): Memory overread secure enclave in Asylo 0.6.2 (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-8940 and fix it if it is affected.

What it is: CVE-2020-8940 is a medium-severity memory corruption vulnerability in Google LLC Asylo, published on 15 Dec 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-8940 in the wild and no public exploit code.

Affected product: Google LLC Asylo. 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-2020-8940/ (Markdown: https://insights.sbomify.com/CVE-2020-8940/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-8940
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-8940
- OSV: https://osv.dev/vulnerability/CVE-2020-8940

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-8940/
Summaries are generated and may contain mistakes; the official description above is the record.