# CVE-2023-46841: xen: Recent x86 CPUs offer functionality named Control-flow Enforcement Technology (CET)

CVE-2023-46841 is fixed in xen on 1 platform, first by DEBIAN-CVE-2023-46841, released March 20, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-46841
- Priority: Routine
- CVSS: 6.5 (medium)
- EPSS: 0.0027
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 20, 2024

## Description

Recent x86 CPUs offer functionality named Control-flow Enforcement Technology (CET).  A sub-feature of this are Shadow Stacks (CET-SS). CET-SS is a hardware feature designed to protect against Return Oriented Programming attacks. When enabled, traditional stacks holding both data and return addresses are accompanied by so called "shadow stacks", holding little more than return addresses.  Shadow stacks aren't writable by normal instructions, and upon function returns their contents are used to check for possible manipulation of a return address coming from the traditional stack.  In particular certain memory accesses need intercepting by Xen.  In various cases the necessary emulation involves kind of replaying of the instruction.  Such replaying typically involves filling and then invoking of a stub.  Such a replayed instruction may raise an exceptions, which is expected and dealt with accordingly.  Unfortunately the interaction of both of the above wasn't right: Recovery involves removal of a call frame from the (traditional) stack. The counterpart of this operation for the shadow stack was missing.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | xen Debian 12.15 (bookworm) | 4.17.5+23-ga4e5191dc0-1 | [DEBIAN-CVE-2023-46841](https://patchblox.com/security/data/fix/linux/debian-cve-2023-46841.md) | Mar 20, 2024 |
| Linux | xen Debian 13.5 (trixie) | 4.17.3+36-g54dacb5c02-1 | [DEBIAN-CVE-2023-46841](https://patchblox.com/security/data/fix/linux/debian-cve-2023-46841.md) | Mar 20, 2024 |
| Linux | xen Debian 14 | 4.17.3+36-g54dacb5c02-1 | [DEBIAN-CVE-2023-46841](https://patchblox.com/security/data/fix/linux/debian-cve-2023-46841.md) | Mar 20, 2024 |

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