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CVE-2025-39684— comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于comedi模块在do_insn_ioctl和do_insnlist_ioctl中使用未初始化内存。

AI Predicted 7.8 Difficulty: Moderate EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1005 · Data from Local System

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux ed9eccbe8970f6eedc1b978c157caf1251a896d4< 868a1b68dcd9f2805bb86aa64862402f785d8c4a affected
ed9eccbe8970f6eedc1b978c157caf1251a896d4< ff4a7c18799c7fe999fa56c5cf276e13866b8c1a affected
ed9eccbe8970f6eedc1b978c157caf1251a896d4< d84f6e77ebe3359394df32ecd97e0d76a25283dc affected
ed9eccbe8970f6eedc1b978c157caf1251a896d4< f3b0c9ec54736f3b8118f93a473d22e11ee65743 affected
ed9eccbe8970f6eedc1b978c157caf1251a896d4< aecf0d557ddd95ce68193a5ee1dc4c87415ff08a affected
ed9eccbe8970f6eedc1b978c157caf1251a896d4< 3cd212e895ca2d58963fdc6422502b10dd3966bb affected
2.6.29 affected
< 2.6.29 unaffected
… +6 more rows
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I. Basic Information for CVE-2025-39684

Vulnerability Information
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Vulnerability Title
comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a KMSAN kernel-infoleak in `do_insn_ioctl()`. A kernel buffer is allocated to hold `insn->n` samples (each of which is an `unsigned int`). For some instruction types, `insn->n` samples are copied back to user-space, unless an error code is being returned. The problem is that not all the instruction handlers that need to return data to userspace fill in the whole `insn->n` samples, so that there is an information leak. There is a similar syzbot report for `do_insnlist_ioctl()`, although it does not have a reproducer for it at the time of writing. One culprit is `insn_rw_emulate_bits()` which is used as the handler for `INSN_READ` or `INSN_WRITE` instructions for subdevices that do not have a specific handler for that instruction, but do have an `INSN_BITS` handler. For `INSN_READ` it only fills in at most 1 sample, so if `insn->n` is greater than 1, the remaining `insn->n - 1` samples copied to userspace will be uninitialized kernel data. Another culprit is `vm80xx_ai_insn_read()` in the "vm80xx" driver. It never returns an error, even if it fails to fill the buffer. Fix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making sure that uninitialized parts of the allocated buffer are zeroed before handling each instruction. Thanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`. That fix replaced the call to `kmalloc_array()` with `kcalloc()`, but it is not always necessary to clear the whole buffer.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于comedi模块在do_insn_ioctl和do_insnlist_ioctl中使用未初始化内存。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux ed9eccbe8970f6eedc1b978c157caf1251a896d4 ~ 868a1b68dcd9f2805bb86aa64862402f785d8c4a -
Linux Linux 2.6.29 -

II. Public POCs for CVE-2025-39684

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III. Intelligence Information for CVE-2025-39684

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Patches & Fixes for CVE-2025-39684 (1)

Same Patch Batch · Linux · 2025-09-05 · 60 CVEs total

CVE-2025-39726 9.8 CRITICAL s390/ism: fix concurrency management in ism_cmd()
CVE-2025-39682 9.8 CRITICAL tls: fix handling of zero-length records on the rx_list
CVE-2025-38734 9.8 CRITICAL net/smc: fix UAF on smcsk after smc_listen_out()
CVE-2025-39702 9.8 CRITICAL ipv6: sr: Fix MAC comparison to be constant-time
CVE-2025-39703 9.8 CRITICAL net, hsr: reject HSR frame if skb can't hold tag
CVE-2025-38737 9.8 CRITICAL cifs: Fix oops due to uninitialised variable
CVE-2025-39673 9.8 CRITICAL ppp: fix race conditions in ppp_fill_forward_path
CVE-2025-39704 8.8 HIGH LoongArch: KVM: Fix stack protector issue in send_ipi_data()
CVE-2025-39718 8.4 HIGH vsock/virtio: Validate length in packet header before skb_put()
CVE-2025-39711 7.8 HIGH media: ivsc: Fix crash at shutdown due to missing mei_cldev_disable() calls
CVE-2025-39710 7.8 HIGH media: venus: Add a check for packet size after reading from shared memory
CVE-2025-39697 7.8 HIGH NFS: Fix a race when updating an existing write
CVE-2025-39714 7.8 HIGH media: usbtv: Lock resolution while streaming
CVE-2025-39717 7.8 HIGH open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE
CVE-2025-39698 7.8 HIGH io_uring/futex: ensure io_futex_wait() cleans up properly on failure
CVE-2025-38731 7.8 HIGH drm/xe: Fix vm_bind_ioctl double free bug
CVE-2025-39696 7.8 HIGH ALSA: hda: tas2781: Fix wrong reference of tasdevice_priv
CVE-2025-39691 7.8 HIGH fs/buffer: fix use-after-free when call bh_read() helper
CVE-2025-39689 7.8 HIGH ftrace: Also allocate and copy hash for reading of filter files
CVE-2025-39677 7.8 HIGH net/sched: Fix backlog accounting in qdisc_dequeue_internal

Showing top 20 of 60 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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