{"cve":"CVE-2024-42240","nvd":{"published":"2024-08-07T16:15:46.810","modified":"2026-06-17T07:49:05.100","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/bhi: Avoid warning in #DB handler due to BHI mitigation\n\nWhen BHI mitigation is enabled, if SYSENTER is invoked with the TF flag set\nthen entry_SYSENTER_compat() uses CLEAR_BRANCH_HISTORY and calls the\nclear_bhb_loop() before the TF flag is cleared. This causes the #DB handler\n(exc_debug_kernel()) to issue a warning because single-step is used outside the\nentry_SYSENTER_compat() function.\n\nTo address this issue, entry_SYSENTER_compat() should use CLEAR_BRANCH_HISTORY\nafter making sure the TF flag is cleared.\n\nThe problem can be reproduced with the following sequence:\n\n  $ cat sysenter_step.c\n  int main()\n  { asm(\"pushf; pop %ax; bts $8,%ax; push %ax; popf; sysenter\"); }\n\n  $ gcc -o sysenter_step sysenter_step.c\n\n  $ ./sysenter_step\n  Segmentation fault (core dumped)\n\nThe program is expected to crash, and the #DB handler will issue a warning.\n\nKernel log:\n\n  WARNING: CPU: 27 PID: 7000 at arch/x86/kernel/traps.c:1009 exc_debug_kernel+0xd2/0x160\n  ...\n  RIP: 0010:exc_debug_kernel+0xd2/0x160\n  ...\n  Call Trace:\n  <#DB>\n   ? show_regs+0x68/0x80\n   ? __warn+0x8c/0x140\n   ? exc_debug_kernel+0xd2/0x160\n   ? report_bug+0x175/0x1a0\n   ? handle_bug+0x44/0x90\n   ? exc_invalid_op+0x1c/0x70\n   ? asm_exc_invalid_op+0x1f/0x30\n   ? exc_debug_kernel+0xd2/0x160\n   exc_debug+0x43/0x50\n   asm_exc_debug+0x1e/0x40\n  RIP: 0010:clear_bhb_loop+0x0/0xb0\n  ...\n  </#DB>\n  <TASK>\n   ? entry_SYSENTER_compat_after_hwframe+0x6e/0x8d\n  </TASK>\n\n  [ bp: Massage commit message. ]","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-835"],"references":["https://git.kernel.org/stable/c/08518d48e5b744620524f0acd7c26c19bda7f513","https://git.kernel.org/stable/c/a765679defe1dc1b8fa01928a6ad6361e72a1364","https://git.kernel.org/stable/c/ac8b270b61d48fcc61f052097777e3b5e11591e0","https://git.kernel.org/stable/c/dae3543db8f0cf8ac1a198c3bb4b6e3c24d576cf","https://git.kernel.org/stable/c/db56615e96c439e13783d7715330e824b4fd4b84"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:53:51.317825789+00:00"},"epss":{"cve":"CVE-2024-42240","score":0.00219,"percentile":0.1246,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}