CVE-2023-37479
Improper sanitization of MXCSR and RFLAGS in OpenEnclave
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
5.3
Improper sanitization of MXCSR and RFLAGS in OpenEnclave
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.
- Record
CVE-2023-37479- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N - Weakness
- CWE-665
- Updated
- 2026-11-02
EUVDEUVD-2023-41368
5.3
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.
- Record
EUVD-2023-41368- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N - Updated
- 2026-11-03
NVD
5.3
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.
- Record
CVE-2023-37479- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-665
- Updated
- 2026-11-02
OSV
5.3
Improper sanitization of MXCSR and RFLAGS in OpenEnclave
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.
- Record
CVE-2023-37479- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N - Weakness
- CWE-665
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-37479 is a medium vulnerability (CVSS 5.3) in Openenclave, published July 17, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.69%, the 53rd percentile. No source names a fixed version.
References
github.com/openenclave/openenclave/security/advisories/GHSA-5gfr-m6mx-p5w4
github.com/openenclave/openenclave/commit/ca54623333875b9beaad92c999a92b015c44b079
intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/best-practices/mxcsr-configuration-dependent-timing.html
github.com/CVEProject/cvelistV5/tree/main/cves/2023/37xxx/CVE-2023-37479.json
nvd.nist.gov/vuln/detail/CVE-2023-37479