CVE-2025-39994 (GCVE-0-2025-39994)
Vulnerability from cvelistv5
Published
2025-10-15 07:58
Modified
2026-08-05 12:06
Severity ?
7.3 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: media: tuner: xc5000: Fix use-after-free in xc5000_release The original code uses cancel_delayed_work() in xc5000_release(), which does not guarantee that the delayed work item timer_sleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000_release() may free the xc5000_priv while timer_sleep is still active and attempts to dereference the xc5000_priv. A typical race condition is illustrated below: CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000_release() | xc5000_do_timer_sleep() cancel_delayed_work() | hybrid_tuner_release_state(priv) | kfree(priv) | | priv = container_of() // UAF Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the timer_sleep is properly canceled before the xc5000_priv memory is deallocated. A deadlock concern was considered: xc5000_release() is called in a process context and is not holding any locks that the timer_sleep work item might also need. Therefore, the use of the _sync() variant is safe here. This bug was initially identified through static analysis. [hverkuil: fix typo in Subject: tunner -> tuner]
References
Impacted products
Vendor Product Version
Linux Linux Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
Version: f7a27ff1fb77e114d1059a5eb2ed1cffdc508ce8
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmedia: tuner: xc5000: Fix use-after-free in xc5000_release\n\nThe original code uses cancel_delayed_work() in xc5000_release(), which\ndoes not guarantee that the delayed work item timer_sleep has fully\ncompleted if it was already running. This leads to use-after-free scenarios\nwhere xc5000_release() may free the xc5000_priv while timer_sleep is still\nactive and attempts to dereference the xc5000_priv.\n\nA typical race condition is illustrated below:\n\nCPU 0 (release thread)                 | CPU 1 (delayed work callback)\nxc5000_release()                       | xc5000_do_timer_sleep()\n  cancel_delayed_work()                |\n  hybrid_tuner_release_state(priv)     |\n    kfree(priv)                        |\n                                       |   priv = container_of() // UAF\n\nReplace cancel_delayed_work() with cancel_delayed_work_sync() to ensure\nthat the timer_sleep is properly canceled before the xc5000_priv memory\nis deallocated.\n\nA deadlock concern was considered: xc5000_release() is called in a process\ncontext and is not holding any locks that the timer_sleep work item might\nalso need. Therefore, the use of the _sync() variant is safe here.\n\nThis bug was initially identified through static analysis.\n\n[hverkuil: fix typo in Subject: tunner -\u003e tuner]"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Both halves are software-local: the attacker arms the 5-second `timer_sleep` work through the local `/dev/dvb/adapterN/frontend0` or `/dev/videoN` device node, and the freeing `dvb_frontend_detach()` path is entered by a local write to `/sys/bus/pci/devices/\u003cdev\u003e/remove`/`unbind` or `rmmod` on the PCIe xc5000 cards (cx23885, cx88, saa7134), with no network, adjacent-network, or remote-peer data path into `xc5000_release()`.\nAC:L - The attacker fully controls the arming side with deterministic timing \u2014 `dvb_shutdown_timeout` defaults to 0, so closing the frontend immediately triggers `xc5000_sleep()` and the work fires exactly 5 s later \u2014 and the callback then executes for roughly 350 ms on cx231xx boards (`msleep(10)+msleep(330)+msleep(10)` in `cx231xx_tuner_callback()`), an enormous window that can be re-armed indefinitely for free; once it is hit, `cancel_delayed_work()` cannot steal a running work item and the use-after-free is unconditional.\nPR:L - Arming the vulnerable work requires nothing more than opening and closing the DVB frontend or V4L2 video node, which systemd tags with `uaccess` (and which is group `video` on media appliances, set-top boxes and DVR/kiosk systems), so an ordinary unprivileged local account suffices; no capability, user namespace, or root is needed on the attacker-controlled side.\nUI:R - Completing the exploit needs the free itself, which only occurs on driver teardown \u2014 an administrator running `rmmod`/`unbind`, or a user unplugging the USB TV tuner \u2014 an action the unprivileged attacker cannot perform, so a separate user must act while the primed work is executing.\nS:U - The corruption is confined to kernel heap objects (the freed `struct xc5000_priv` and whatever reclaims its kmalloc-192 slot) within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - `xc5000_do_timer_sleep()` reads `priv-\u003efe` out of the freed slab and `xc5000_tuner_reset()` then dereferences `fe-\u003edvb`, `fe-\u003edvb-\u003epriv` and `priv-\u003ei2c_props.adap-\u003ealgo_data`, so spraying the kmalloc-192 cache turns the dangling pointer into an arbitrary-address read chain and leaks kernel pointers that defeat KASLR.\nI:H - `xc5000_tuner_reset()` performs `fe-\u003ecallback(...)` where `fe` was loaded from the freed object, giving a fully attacker-controlled indirect call with a controlled first argument once the slab is reclaimed \u2014 a direct control-flow hijack primitive, not merely a stray read.\nA:H - Dereferencing the freed `xc5000_priv` from workqueue context reliably produces a KASAN slab-use-after-free splat and an oops/panic (and the bogus function-pointer call faults in kernel context), taking the system down."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:06:59.351Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bc4ffd962ce16a154c44c68853b9d93f5b6fc4b8"
        },
        {
          "url": "https://git.kernel.org/stable/c/e2f5eaafc0306a76fb1cb760aae804b065b8a341"
        },
        {
          "url": "https://git.kernel.org/stable/c/3f876cd47ed8bca1e28d68435845949f51f90703"
        },
        {
          "url": "https://git.kernel.org/stable/c/df0303b4839520b84d9367c2fad65b13650a4d42"
        },
        {
          "url": "https://git.kernel.org/stable/c/71ed8b81a4906cb785966910f39cf7f5ad60a69e"
        },
        {
          "url": "https://git.kernel.org/stable/c/effb1c19583bca7022fa641a70766de45c6d41ac"
        },
        {
          "url": "https://git.kernel.org/stable/c/9a00de20ed8ba90888479749b87bc1532cded4ce"
        },
        {
          "url": "https://git.kernel.org/stable/c/4266f012806fc18e46da4a04d130df59a4946f93"
        },
        {
          "url": "https://git.kernel.org/stable/c/40b7a19f321e65789612ebaca966472055dab48c"
        }
      ],
      "title": "media: tuner: xc5000: Fix use-after-free in xc5000_release",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39994",
    "datePublished": "2025-10-15T07:58:19.503Z",
    "dateReserved": "2025-04-16T07:20:57.150Z",
    "dateUpdated": "2026-08-05T12:06:59.351Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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