CVE-2026-98044 (GCVE-0-2026-98044)
Vulnerability from cvelistv5
Published
2026-09-25 10:23
Modified
2026-10-21 12:54
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Reject legacy packet loads from callbacks check_ld_abs() models a failed BPF_LD_ABS or BPF_LD_IND in a subprogram as an implicit return with R0 set to zero. It calls prepare_func_exit() to explore this synthesized path. When the load is reached directly from a synchronous callback, prepare_func_exit() enforces the callback return contract and marks R0 precise. R0 is not derived from a real instruction on this path, so precision backtracking reaches the callback call with R0 still requested and triggers the "callback unexpected regs" verifier bug. A privileged program loader can therefore cause a verifier warning and an -EFAULT BPF_PROG_LOAD. These legacy packet-load instructions are deprecated. Reject them from callbacks rather than complicating their implicit-return model. Check all active frames before constructing the implicit return so nested static subprograms cannot hide the callback context. Global functions are verified independently with a fresh frame zero, so an active-frame check cannot identify a global function called from a callback. Also check the complete subprogram call graph during stack-depth validation and reject a function containing a legacy load when any caller is a callback. This covers global and static descendants without making has_ld_abs transitive, preserving its per-function BTF return-type check. Ordinary uses outside callbacks remain supported.
References
Impacted products
Vendor Product Version
Linux Linux Version: 8674e2db06cff6b50f2216eed9a761d15425bb34
Version: ce01a4e5cfac7adbe0be565f90cd32ecbb2f8337
Version: ee861486e377edc55361c08dcbceab3f6b6577bd
Version: ee861486e377edc55361c08dcbceab3f6b6577bd
Version: 928d354ae3557e8f755a227e67be88034eb3cd7f
Version: 8a800497d9f6c2ec9c2c1ba7b71d0ac2ea7f7bbe
Version: de1055e7f9e67af32b1f3376066272b04e5223c0
Version: 37ad2bb11e9de92cb7b94548705eeedd87f7d392
Version: d846d83bdacbd8f14fc45c63b8c1d22608452e1c
Version: 6.12.101   ≤
Version: 6.18.42   ≤
Version: 5.10.265   ≤
Version: 5.15.216   ≤
Version: 6.1.183   ≤
Version: 6.6.148   ≤
Version: 7.0.10   ≤
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject legacy packet loads from callbacks\n\ncheck_ld_abs() models a failed BPF_LD_ABS or BPF_LD_IND in a\nsubprogram as an implicit return with R0 set to zero. It calls\nprepare_func_exit() to explore this synthesized path.\n\nWhen the load is reached directly from a synchronous callback,\nprepare_func_exit() enforces the callback return contract and marks R0\nprecise. R0 is not derived from a real instruction on this path, so\nprecision backtracking reaches the callback call with R0 still requested\nand triggers the \"callback unexpected regs\" verifier bug. A privileged\nprogram loader can therefore cause a verifier warning and an -EFAULT\nBPF_PROG_LOAD.\n\nThese legacy packet-load instructions are deprecated. Reject them from\ncallbacks rather than complicating their implicit-return model. Check all\nactive frames before constructing the implicit return so nested static\nsubprograms cannot hide the callback context.\n\nGlobal functions are verified independently with a fresh frame zero, so\nan active-frame check cannot identify a global function called from a\ncallback. Also check the complete subprogram call graph during stack-depth\nvalidation and reject a function containing a legacy load when any caller\nis a callback. This covers global and static descendants without making\nhas_ld_abs transitive, preserving its per-function BTF return-type check.\nOrdinary uses outside callbacks remain supported."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:54:12.833Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/e7d28823c662128caae63f14e16bd394916c139b"
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      "title": "bpf: Reject legacy packet loads from callbacks",
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    "cveId": "CVE-2026-98044",
    "datePublished": "2026-09-25T10:23:55.454Z",
    "dateReserved": "2026-09-25T10:19:56.071Z",
    "dateUpdated": "2026-10-21T12:54:12.833Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2"
}


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