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CVE-2023-37479

Improper sanitization of MXCSR and RFLAGS in OpenEnclave

HIGH
7.5
CVSS Score
Published: July 17, 2023 at 10:13 PM UTC
Updated: June 17, 2026 at 06:08 AM UTC
1 product affected across 1 vendorOpenenclave

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Severity
HIGH7.5
Exploit prediction
EPSS 0.7%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Openenclave· Openenclave
95%
v < 0.19.3
Affected range stops below 0.19.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (3)

x_refsource_MISCPatch
Source: [email protected]
https://github.com/openenclave/openenclave/commit/ca54623333875b9beaad92c999a92b015c44b079
x_refsource_CONFIRMVendor Advisory
Source: [email protected]
https://github.com/openenclave/openenclave/security/advisories/GHSA-5gfr-m6mx-p5w4
x_refsource_MISCTechnical Description
Source: [email protected]
https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/best-practices/mxcsr-configuration-dependent-timing.html

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-665

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