Local CPU dead loop via uncleared WFE state
Published Jan 6, 2025 · Updated May 11, 2026
Denial of service in the Linux kernel on x86 FRED systems allows local users to trap a CPU in a dead loop via a #CP fault. The !ibt_fatal continuation path restores execution without clearing the interrupted context's WAIT_FOR_ENDBRANCH state, so the resumed instruction immediately raises another missing-ENDBRANCH #CP. Reachability requires FRED hardware with kernel IBT enabled and a recoverable missing-ENDBRANCH fault; the loop interrupts service on the affected CPU.
Summary
What happened
Denial of service in the Linux kernel on x86 FRED systems allows local users to trap a CPU in a dead loop via a #CP fault. The !ibt_fatal continuation path restores execution without clearing the interrupted context's WAIT_FOR_ENDBRANCH state, so the resumed instruction immediately raises another missing-ENDBRANCH #CP. Reachability requires FRED hardware with kernel IBT enabled and a recoverable missing-ENDBRANCH fault; the loop interrupts service on the affected CPU.
The record
- CVE
- CVE-2024-56761
- Published
- Jan 6, 2025
- Updated
- May 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499.004
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jan 6, 2025CVE publishedPublication date reported by the CVE source.
- May 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=6.6
- Affected versionversion=a5f6c2ace9974adf92ce65dacca8126d90adabfe <151447859d6fb0dcce8259f0971c6e94fb801661
- Affected versionversion=a5f6c2ace9974adf92ce65dacca8126d90adabfe <b939f108e86b76119428a6fa4e92491e09ac7867
- Affected versionversion=a5f6c2ace9974adf92ce65dacca8126d90adabfe <dc81e556f2a017d681251ace21bf06c126d5a192
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What is affected?
Published CVSS scores
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Attacks
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