{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "a6c22c91b6284e4713c0cf5b20ab3c9c71b77ae8"
            },
            {
              "fixed": "617c8266e49f45747f71e74177646a63f72b7025"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "e3245f8990431950d20631c72236d4e8cb2dcde8"
            },
            {
              "fixed": "96d31b28263c429a56e4de85bcf744a5c320b3a3"
            },
            {
              "fixed": "266aa4ad0b2e82397cd9045752c9bff03d98eddd"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "6.18.2"
            },
            {
              "fixed": "6.18.53"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.18.53"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98061.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject tail calls directly from callback frames\n\nA tail call from a non-zero frame is modeled as a return from that frame.\nThe verifier makes R0 unknown and calls prepare_func_exit() for the taken\nbranch.\n\nWhen the current frame is a synchronous callback, prepare_func_exit()\nenforces the callback return-value contract and marks R0 precise. Since the\ntail-call path synthesized R0 rather than deriving it from an instruction,\nprecision backtracking reaches the callback-calling instruction with R0\nstill requested and triggers the \"callback unexpected regs\" verifier bug.\nA CAP_BPF task can therefore cause a WARN and an -EFAULT BPF_PROG_LOAD.\n\nTail calls reachable from callbacks are already rejected later by\ncheck_max_stack_depth(). Reject a tail call made directly by a callback\nbefore constructing the inconsistent return state, using the existing\ndiagnostic. Tail calls from ordinary subprograms keep their current\nbehavior.",
  "id": "CVE-2026-98061",
  "modified": "2026-09-27T03:30:56.408161277Z",
  "published": "2026-09-25T10:24:06.001Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/266aa4ad0b2e82397cd9045752c9bff03d98eddd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/617c8266e49f45747f71e74177646a63f72b7025"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/96d31b28263c429a56e4de85bcf744a5c320b3a3"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98061.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98061"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "bpf: Reject tail calls directly from callback frames"
}