CVE-2026-93164: Software Security Vulnerability Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r7c2-7rh7-h943",
  "modified" : "2026-10-15T12:30:52Z",
  "published" : "2026-09-17T18:32:12Z",
  "aliases" : [ "CVE-2026-93164" ],
  "details" : "In the Linux kernel, the following vulnerability has been resolved:\n\nuprobes/x86: Move optimized uprobe from nop5 to nop10\n\nAndrii reported an issue with optimized uprobes [1] that can clobber\nredzone area with call instruction storing return address on stack\nwhere user code may keep temporary data without adjusting rsp.\n\nFixing this by moving the optimized uprobes on top of 10-bytes nop\ninstruction, so we can squeeze another instruction to escape the\nredzone area before doing the call, like:\n\n  lea -0x80(%rsp), %rsp\n  call tramp\n\nNote the lea instruction is used to adjust the rsp register without\nchanging the flags.\n\nWe use nop10 and following transformation to optimized instructions\nabove and back as suggested by Peterz [2].\n\nOptimize path (int3_update_optimize):\n\n  1) Initial state after set_swbp() installed the uprobe:\n      cc 2e 0f 1f 84 00 00 00 00 00\n\n     From offset 0 this is INT3 followed by the tail of the original\n     10-byte NOP.\n\n     After a previous unoptimization bytes 5..9 may still contain the\n     old call instruction, which remains valid for threads already there.\n\n  2) Rewrite the LEA tail and call displacement:\n      cc [8d 64 24 80 e8 d0 d1 d2 d3]\n\n     From offset 0 this traps on the uprobe INT3.  Bytes 1..9 are not\n     executable entry points while byte 0 is trapped.\n\n  3) Publish the first LEA byte:\n      [48] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this is:\n        lea -0x80(%rsp), %rsp\n        call <uprobe-trampoline>\n\nUnoptimize path (int3_update_unoptimize):\n\n  1) Initial optimized state:\n      48 8d 64 24 80 e8 d0 d1 d2 d3\n     Same as 3) above.\n\n  2) Trap new entries before restoring the NOP bytes:\n      [cc] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this traps. A thread that had already executed the\n     LEA can still reach the intact CALL at offset 5.\n\n  3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped\n     and byte 5 as CALL.\n      cc [2e 0f 1f 84] e8 d0 d1 d2 d3\n\n     From offset 0 this still traps. Offset 5 is still the CALL for any\n     thread that was already past the first LEA byte.\n\n  4) Publish the first byte of the original NOP:\n      [66] 2e 0f 1f 84 e8 d0 d1 d2 d3\n\n     From offset 0 this is the restored 10-byte NOP; the CALL opcode and\n     displacement are now only NOP operands.  Offset 5 still decodes as\n     CALL for a thread that was already there.\n\n     Tthere is only a single target uprobe-trampoline for the given nop10\n     instruction address, so the CALL instruction will not be changed across\n     unoptimization/optimization cycles.\n     Therefore, any task that is preempted at the CALL instruction is guaranteed\n     to observe that CALL and not anything else.\n\nNote as explained in [2] we need to use following nop10:\n       PF1   PF2   ESC   NOPL  MOD   SIB   DISP32\nNOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1)\n\nwhich means we need to allow 0x2e prefix which maps to INAT_PFX_CS\nattribute in is_prefix_bad function.\n\nAlso changing the uprobe syscall error when called out of uprobe\ntrampoline to -EPROTO, so we are able to detect the fixed kernel.\n\nThe optimized uprobe performance stays the same:\n\n        uprobe-nop     :    3.129 ± 0.013M/s\n        uprobe-push    :    3.045 ± 0.006M/s\n        uprobe-ret     :    1.095 ± 0.004M/s\n  -->   uprobe-nop10   :    7.170 ± 0.020M/s\n        uretprobe-nop  :    2.143 ± 0.021M/s\n        uretprobe-push :    2.090 ± 0.000M/s\n        uretprobe-ret  :    0.942 ± 0.000M/s\n  -->   uretprobe-nop10:    3.381 ± 0.003M/s\n        usdt-nop       :    3.245 ± 0.004M/s\n  -->   usdt-nop10     :    7.256 ± 0.023M/s\n\n[1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/\n[2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t",
  "severity" : [ ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-93164"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/1b3fecd09910040668b752f3377d7218ca5c59ac"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/554ba38456dad8053a1a80afe6ae6da9eff745cc"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/7abc9b49ad01a179e893ba137364a560e21b09f8"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : null,
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-09-17T17:18:11Z"
  }
}