rxrpc: fix RESPONSE authenticator parser OOB read

{
  "id": "e50694350e17a84a683559baa11cc2e2191948fe4a92ff95da6be654f328e28f",
  "url": "https://osv.dev/vulnerability/CVE-2026-31636",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "rxrpc: fix RESPONSE authenticator parser OOB read",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: rxrpc: fix RESPONSE authenticator parser OOB read rxgk_verify_authenticator() copies auth_len bytes into a temporary buffer and then passes p + auth_len as the parser limit to rxgk_do_verify_authenticator(). Since p is a __be32 *, that inflates the parser end pointer by a factor of four and lets malformed RESPONSE authenticators read past the kmalloc() buffer. Decoded from the original latest-net reproduction logs with scripts/decode_stacktrace.sh: BUG: KASAN: slab-out-of-bounds in rxgk_verify_response() Call Trace: dump_stack_lvl() [lib/dump_stack.c:123] print_report() [mm/kasan/report.c:379 mm/kasan/report.c:482] kasan_report() [mm/kasan/report.c:597] rxgk_verify_response() [net/rxrpc/rxgk.c:1103 net/rxrpc/rxgk.c:1167 net/rxrpc/rxgk.c:1274] rxrpc_process_connection() [net/rxrpc/conn_event.c:266 net/rxrpc/conn_event.c:364 net/rxrpc/conn_event.c:386] process_one_work() [kernel/workqueue.c:3281] worker_thread() [kernel/workqueue.c:3353 kernel/workqueue.c:3440] kthread() [kernel/kthread.c:436] ret_from_fork() [arch/x86/kernel/process.c:164] Allocated by task 54: rxgk_verify_response() [include/linux/slab.h:954 net/rxrpc/rxgk.c:1155 net/rxrpc/rxgk.c:1274] rxrpc_process_connection() [net/rxrpc/conn_event.c:266 net/rxrpc/conn_event.c:364 net/rxrpc/conn_event.c:386] Convert the byte count to __be32 units before constructing the parser limit.",
    "evidence": "osv:CVE-2026-31636",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.23",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.13",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-31636",
      "aliases": [
        "CVE-2026-31636"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H"
        }
      ],
      "affected": [
        {
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "7875f3d9777bd4e9892c4db830571ab8ac2044c0"
                },
                {
                  "fixed": "20a188775a9a9982d1987e12660d9b44b40a6c99"
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                {
                  "fixed": "3e3138007887504ee9206d0bfb5acb062c600025"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31636.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.16.0"
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                {
                  "fixed": "6.18.23"
                }
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            },
            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.19.0"
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                {
                  "fixed": "6.19.13"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31636.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:48.106642792Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/20a188775a9a9982d1987e12660d9b44b40a6c99",
        "https://git.kernel.org/stable/c/3e3138007887504ee9206d0bfb5acb062c600025",
        "https://git.kernel.org/stable/c/7875f3d9777bd4e9892c4db830571ab8ac2044c0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31636.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31636",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31636.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31636",
        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 515849,
  "published_at": "2026-04-24T14:44:50.637+00:00"
}