# CVE-2023-37479: Improper sanitization of MXCSR and RFLAGS in OpenEnclave

> Attackers can exploit unsanitized CPU registers in Open Enclave to perform side-channel attacks and leak sensitive data from enclaves.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N`)
- **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:** No
- **Published:** 17 Jul 2023
- **Updated:** 10 Oct 2024
- **Also known as:** GHSA-5gfr-m6mx-p5w4

## What is CVE-2023-37479?

CVE-2023-37479 is a medium-severity vulnerability in openenclave, published on 17 Jul 2023. 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

Open Enclave is a hardware-agnostic open source library for developing applications that utilize Hardware-based Trusted Execution Environments, also known as Enclaves. There are two issues that are mitigated in version 0.19.3. First, Open Enclave SDK does not properly sanitize the `MXCSR` register on enclave entry. This makes applications vulnerable to MXCSR Configuration Dependent Timing (MCDT) attacks, where incorrect `MXCSR` values can impact instruction retirement by at most one cycle, depending on the (secret) data operand value. Please find more details in the guidance from Intel in the references. Second, Open Enclave SDK does not sanitize x86's alignment check flag `RFLAGS.AC` on enclave entry. This opens up the possibility for a side-channel attacker to be notified for every unaligned memory access performed by the enclave. The issue has been addressed in version 0.19.3 and the current master branch. Users will need to recompile their applications against the patched libraries to be protected from this vulnerability. There are no known workarounds for this vulnerability.

Weakness: CWE-665 (Improper Initialization)

## Which versions are affected by CVE-2023-37479?

It affects 1 product.


Products: Openenclave Openenclave.

## How do I fix CVE-2023-37479?

No fix has been published for CVE-2023-37479 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-37479 being exploited?

There is no known exploitation of CVE-2023-37479 in the wild and no public exploit code.

## Other vulnerabilities in openenclave

- [CVE-2020-15224](https://insights.sbomify.com/CVE-2020-15224/): Socket syscalls can leak enclave memory contents in Open Enclave (medium 6.8)
- [CVE-2020-15107](https://insights.sbomify.com/CVE-2020-15107/): x87 FPU operations in enclaves are vulnerable to ABI poisoning in openenclave (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-37479 and fix it if it is affected.

What it is: CVE-2023-37479 is a medium-severity vulnerability in openenclave, published on 17 Jul 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-37479 in the wild and no public exploit code.

Affected product: openenclave. 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-2023-37479/ (Markdown: https://insights.sbomify.com/CVE-2023-37479/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-37479
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-37479
- OSV: https://osv.dev/vulnerability/CVE-2023-37479

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-37479/
Summaries are generated and may contain mistakes; the official description above is the record.