CVE-2023-46841

Summary

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.

Affected Software

VendorProductVersion RangeStatus
XenXenconsult Xen advisory XSA-451unknown

Weaknesses

Workarounds

While in principle it is possible to disable use of CET on capable systems using the "cet=no-shstk" command line option, doing so disables an important security feature and may therefore not be advisable.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

CVE Program Container

Additional References

References