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CVE-2026-68438— smp: Make CSD lock acquisition atomic for debug mode

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基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于CSD锁获取操作缺乏原子性，多个发送者可能并发修改同一目标CPU的CSD数据，导致回调字段被覆盖及节点重复入队，可能造成内核软锁警告或崩溃。

AI Predicted 5.5 Difficulty: Theoretical EPSS 0.20% · P9

Possible ATT&CK Techniques 1 AI

T1053 · Scheduled Task/Job

Affected Version Matrix 6

VendorProduct Version RangeStatus
Linux Linux b0473dcd4b1d7e2e44947e7ac1820c73a268821a< 282d220bae5fbfc90cf0e3d5b5e42c00ad79f989 affected
b0473dcd4b1d7e2e44947e7ac1820c73a268821a< 35551efb155e3b83445a6c3f66cb498d5efc182c affected
7.1 affected
< 7.1 unaffected
7.1.6≤ 7.1.* unaffected
7.2≤ * unaffected
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I. Basic Information for CVE-2026-68438

Vulnerability Information
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Vulnerability Title
smp: Make CSD lock acquisition atomic for debug mode
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smp: Make CSD lock acquisition atomic for debug mode Commit b0473dcd4b1d ("smp: Improve smp_call_function_single() CSD-lock diagnostics") changed smp_call_function_single() so that, when CSD lock debugging is enabled, async !wait calls use the destination CPU csd_data. That improves diagnostics, but it also removes the single-writer property that made the old csd_lock() safe: multiple CPUs can now prepare the same destination CPU CSD concurrently. csd_lock() currently waits for CSD_FLAG_LOCK to clear and then sets the bit with a non-atomic read-modify-write. Two senders can both see an unlocked CSD, set the bit, overwrite the callback fields, and enqueue the same llist node. Re-adding a node that is already the queue head can make node->next point to itself, leaving the target CPU stuck walking call_single_queue. Later synchronous work, such as a TLB shootdown, can then remain queued and trigger soft-lockup warnings or panics. Keep the single csd_lock() implementation, but when CSD lock debugging is enabled, acquire CSD_FLAG_LOCK with try_cmpxchg_acquire(). This makes the destination CPU CSD a real atomic lock in the only configuration where it can be shared by multiple remote senders, while preserving the existing non-debug fast path.
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基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于CSD锁获取操作缺乏原子性，多个发送者可能并发修改同一目标CPU的CSD数据，导致回调字段被覆盖及节点重复入队，可能造成内核软锁警告或崩溃。
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 b0473dcd4b1d7e2e44947e7ac1820c73a268821a ~ 282d220bae5fbfc90cf0e3d5b5e42c00ad79f989 -
Linux Linux 7.1 -

II. Public POCs for CVE-2026-68438

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III. Intelligence Information for CVE-2026-68438

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Patches & Fixes for CVE-2026-68438 (2)

Same Patch Batch · Linux · 2026-08-12 · 22 CVEs total

CVE-2026-68431 9.1 CRITICAL ksmbd: validate minimum PDU size for transform requests
CVE-2026-68432 8.8 HIGH vxlan: require CAP_NET_ADMIN in the device netns for changelink
CVE-2026-68433 8.6 HIGH libceph: bound get_version reply decode to front len
CVE-2026-68446 7.8 HIGH drm/vmwgfx: Validate vmw_surface_metadata::array_size
CVE-2026-68445 7.8 HIGH drm/vc4: Prevent shader BO mappings from becoming writable
CVE-2026-68440 7.8 HIGH net: txgbe: fix heap overflow when reading module EEPROM
CVE-2026-68442 7.8 HIGH btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps
CVE-2026-68447 7.1 HIGH drm/amdkfd: clamp v9 CRIU control stack checkpoint copy to BO size
CVE-2026-68450 btrfs: free mapping node on duplicate reloc root insert
CVE-2026-68429 drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()
CVE-2026-68449 ata: sata_dwc_460ex: fix infinite loop in NCQ tag completion bit-scanning
CVE-2026-68448 ovl: check access to copy_file_range source with src mounter creds
CVE-2026-68444 firmware: arm_ffa: Fix NULL dereference in ffa_partition_info_get()
CVE-2026-68443 hwmon: (gigabyte_waterforce) Stop device IO before calling hid_hw_stop
CVE-2026-68441 net/sched: Handle TC_ACT_REDIRECT from qdisc filter chains
CVE-2026-68439 wifi: mt76: mt7925: fix possible NULL-pointer deref in mt7925_mcu_bss_he_tlv()
CVE-2026-68437 drm/imagination: Fit paired fragment job in the correct CCCB
CVE-2026-68436 drm/amd/display: use kvzalloc to allocate struct dc
CVE-2026-68435 LoongArch: Fix address space mismatch in kexec command line lookup
CVE-2026-68434 serial: 8250_mid: Fix NULL function pointer dereference on DNV/ICX-D/SNR platforms

Showing top 20 of 22 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-68438

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