{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-74687",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-74687"
  ],
  "published": "2026-08-22T15:32:12Z",
  "summary": "watchdog: at91sam9_wdt: prevent timer rearm during teardown",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nwatchdog: at91sam9_wdt: prevent timer rearm during teardown\n\nat91_ping() rearms the watchdog timer from its callback. timer_delete()\nneither waits for a running callback nor prevents it from rearming the\ntimer, so probe failure or driver removal can leave the timer accessing the\ndevm-allocated at91wdt after it has been freed.\n\nUse timer_shutdown_sync() on both teardown paths. It waits for a running\ncallback and rejects any attempt by the callback to rearm the timer.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": null,
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-74687"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/29fe74c9aa69d78c1c6a3930f1d9fc5db71a6eed"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b7949b0a7d998013b7ec8617a0ef5b07cca80be4"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/8444d66aa6b6e7fe0a26fa1a00a11cb4d0523783"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-25T05:42:41Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The bug is in the AT91SAM9 platform watchdog driver during probe-failure cleanup or driver removal; it is reached only via local kernel/platform actions (boot probe, module load/unload, sysfs bind/unbind), not from network, Bluetooth, or physical USB/serial input paths.\nAC:L - at91_ping() unconditionally re-arms with mod_timer() while timer_delete() neither waits for the callback nor blocks rearm; an attacker who can time teardown or trigger the automatic probe-failure path can reliably race the periodic jiffies callback without uncontrollable layout or victim state.\nPR:L - Per CNA driver timer-teardown UAF precedent, once mod_timer() arms at91_ping() the callback runs autonomously; the UAF is reachable from local probe-failure cleanup or driver-removal activity on AT91 embedded/industrial targets without requiring init-namespace root privileges.\nUI:N - No victim interaction is required; the kernel timer fires on its own schedule and the use-after-free occurs during automatic init-failure teardown or driver removal, independent of opening /dev/watchdog or other user actions.\nS:U - Impact is a kernel heap/timer use-after-free within the host kernel on an embedded AT91 SoC; it does not cross VM, container, or IOMMU security boundaries.\nC:H - The at91_ping() timer callback dereferences freed at91wdt fields (next_heartbeat, wdd, heartbeat, base) after devm release, providing sprayable arbitrary kernel memory disclosure per UAF guidance.\nI:H - Reuse of the freed at91wdt lets at91_wdt_reset() issue MMIO writes through a controlled base pointer and mod_timer() corrupt timer/heap metadata, enabling arbitrary write and control-flow hijack primitives.\nA:H - Use-after-free access from the timer softirq path to freed at91wdt memory causes kernel oops or panic even without deliberate exploitation, and can be repeated by cycling probe/removal against the still-rearming timer."
    }
  }
}