{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2024-35887",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2024-35887"
  ],
  "published": "2024-05-19T08:35:32Z",
  "summary": "ax25: fix use-after-free bugs caused by ax25_ds_del_timer",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: fix use-after-free bugs caused by ax25_ds_del_timer\n\nWhen the ax25 device is detaching, the ax25_dev_device_down()\ncalls ax25_ds_del_timer() to cleanup the slave_timer. When\nthe timer handler is running, the ax25_ds_del_timer() that\ncalls del_timer() in it will return directly. As a result,\nthe use-after-free bugs could happen, one of the scenarios\nis shown below:\n\n      (Thread 1)          |      (Thread 2)\n                          | ax25_ds_timeout()\nax25_dev_device_down()    |\n  ax25_ds_del_timer()     |\n    del_timer()           |\n  ax25_dev_put() //FREE   |\n                          |  ax25_dev-> //USE\n\nIn order to mitigate bugs, when the device is detaching, use\ntimer_shutdown_sync() to stop the timer.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2024-35887"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/28f2d36ac52225a13e020c2589833f1816a0cfc6"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/8a912ef5b7c5d14fb41b9a7935d1df5bb87058bf"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/74204bf9050f7627aead9875fe4e07ba125cb19b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c6a368f9c7af4c14b14d390c2543af8001c9bdb9"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/fd819ad3ecf6f3c232a06b27423ce9ed8c20da89"
    }
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  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-09-14T12:06:03Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 8.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:A - The DAMA slave timer that is used after free is armed and repeatedly re-armed solely by frames from a remote AX.25 peer (SABM with the DAMA bit at net/ax25/ax25_in.c:407, and DAMA polls via ax25_ds_enquiry_response() \u2192 mod_timer()), reached over a point-to-point RF link or bpqether on the local Ethernet segment.\nAC:L - The attacker fully controls the racing side \u2014 keeping a DAMA-slave link up makes ax25_ds_timeout() fire every second and lets the attacker drive mod_timer() from the RX softirq at frame rate, so the window against ax25_dev_device_down()'s non-synchronous del_timer() can be hammered until it is hit, and a single re-arm after the free leaves an armed timer in freed memory.\nPR:N - AX.25 has no authentication whatsoever \u2014 the attacker only needs to transmit frames to a listening AX.25 port to turn on DAMA slave mode and arm the device timer; no account or credential on the target is involved.\nUI:N - No victim action on attacker-supplied content is needed; the free is triggered by a routine port/interface teardown (script-driven port cycling, TNC/serial or bpqether underlying device going down, module unload) while the attacker-maintained timer is active.\nS:U - The corruption is confined to kernel heap memory managed by the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed ax25_dev is a kfree'd slab object that can be reallocated and read back through the still-live timer handler, and the surviving armed timer_list gives an attacker-influenced read of freed/reallocated memory usable for kernel address and data disclosure.\nI:H - mod_timer() on the freed object writes into reallocated memory, and the timer core later loads and calls ->function from the freed ax25_dev, yielding a heap-spray-based control-flow hijack primitive and arbitrary kernel memory modification.\nA:H - Even unexploited, dereferencing and re-arming a timer embedded in freed memory reliably causes slab corruption, list corruption, and kernel oops/panic, taking the system down."
    }
  }
}