High severity · published Sep 5, 2025
CVE-2025-39686
comedi: Make insn_rw_emulate_bits() do insn->n samples
7.8
CVSS
0.2%
EPSS
No
On KEV
Description
In the Linux kernel, the following vulnerability has been resolved:
comedi: Make insn_rw_emulate_bits() do insn->n samples
The `insn_rw_emulate_bits()` function is used as a default handler for
`INSN_READ` instructions for subdevices that have a handler for
`INSN_BITS` but not for `INSN_READ`. Similarly, it is used as a default
handler for `INSN_WRITE` instructions for subdevices that have a handler
for `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the
`INSN_READ` or `INSN_WRITE` instruction handling with a constructed
`INSN_BITS` instruction. However, `INSN_READ` and `INSN_WRITE`
instructions are supposed to be able read or write multiple samples,
indicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently
only handles a single sample. For `INSN_READ`, the comedi core will
copy `insn->n` samples back to user-space. (That triggered KASAN
kernel-infoleak errors when `insn->n` was greater than 1, but that is
being fixed more generally elsewhere in the comedi core.)
Make `insn_rw_emulate_bits()` either handle `insn->n` samples, or return
an error, to conform to the general expectation for `INSN_READ` and
`INSN_WRITE` handlers.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 9% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
2.6.29 before 5.15.190; 5.16 before 6.1.149; 6.2 before 6.6.103; 6.7 before 6.12.44; 6.13 before 6.16.4; 6.17; +1 more · source: NVD
LI
Linux · Linux
ed9eccbe8970f6eedc1b978c157caf1251a896d4 before ab77e85bd3bc006ef40738f26f446a660813da44; ed9eccbe8970f6eedc1b978c157caf1251a896d4 before ae8bc1f07bcb31b8636420e03d1f9c3df6219a2b; ed9eccbe8970f6eedc1b978c157caf1251a896d4 before 842f307a1d115b24f2bcb2415c4e344f11f55930; ed9eccbe8970f6eedc1b978c157caf1251a896d4 before 92352ed2f9ac422181e381c2430c2d0dfb46faa0; ed9eccbe8970f6eedc1b978c157caf1251a896d4 before dc0a2f142d655700db43de90cb6abf141b73d908; ed9eccbe8970f6eedc1b978c157caf1251a896d4 before 7afba9221f70d4cbce0f417c558879cba0eb5e66; +1 more · source: vendor
DL
Debian Linux · Debian
11.0 · source: NVD
SC
SIMATIC CN 4100 · Siemens
before V5.0 · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-39686
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-39686
Patch
https://git.kernel.org/stable/c/7afba9221f70d4cbce0f417c558879cba0eb5e66
Patch
https://git.kernel.org/stable/c/842f307a1d115b24f2bcb2415c4e344f11f55930
Patch
https://git.kernel.org/stable/c/92352ed2f9ac422181e381c2430c2d0dfb46faa0
Patch
https://git.kernel.org/stable/c/ab77e85bd3bc006ef40738f26f446a660813da44
Patch
https://git.kernel.org/stable/c/ae8bc1f07bcb31b8636420e03d1f9c3df6219a2b
Patch
https://git.kernel.org/stable/c/dc0a2f142d655700db43de90cb6abf141b73d908
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