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CVE Record

CVE-2025-38621: md: make rdev_addable usable for rcu mode

In the Linux kernel, the following vulnerability has been resolved: md: make rdev_addable usable for rcu mode Our testcase trigger panic: BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... Oops: Oops: 0000 [#1] SMP NOPTI CPU: 2 UID: 0 PID: 85 Comm: kworker/2:1 Not tainted 6.16.0+ #94 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Workqueue: md_misc md_start_sync RIP: 0010:rdev_addable+0x4d/0xf0 ... Call Trace: <TASK> md_start_sync+0x329/0x480 process_one_work+0x226/0x6d0 worker_thread+0x19e/0x340 kthread+0x10f/0x250 ret_from_fork+0x14d/0x180 ret_from_fork_asm+0x1a/0x30 </TASK> Modules linked in: raid10 CR2: 00000000000000e0 ---[ end trace 0000000000000000 ]--- RIP: 0010:rdev_addable+0x4d/0xf0 md_spares_need_change in md_start_sync will call rdev_addable which protected by rcu_read_lock/rcu_read_unlock. This rcu context will help protect rdev won't be released, but rdev->mddev will be set to NULL before we call synchronize_rcu in md_kick_rdev_from_array. Fix this by using READ_ONCE and check does rdev->mddev still alive.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can crash a system using the md RAID subsystem when a race leaves a device pointer without its expected parent. The public record describes a kernel panic, not data theft or remote code execution. Business urgency depends on whether affected kernels and md RAID are used on critical hosts.

Executive priority

Treat this as an availability risk for Linux storage hosts, not a confirmed breach issue. Prioritize remediation where md RAID backs business-critical systems, clustering, backup infrastructure, or recovery paths.

Technical view

In md, rdev_addable ran under RCU protection, but rdev->mddev could be set to NULL before synchronize_rcu in md_kick_rdev_from_array. md_start_sync could then dereference NULL, causing a kernel oops. The fix uses READ_ONCE and checks that rdev->mddev is still valid.

Likely exposure

Exposure is most plausible on Linux systems running affected kernel versions with the md software RAID subsystem active. The source bundle lists Linux as affected and references versions around 6.7, 6.16.1, and 6.17, but exact downstream distribution status requires vendor confirmation.

Exploitation context

The sources describe a testcase-triggered panic in a QEMU environment and show raid10 loaded. They do not state active exploitation, remote reachability, privilege requirements, or a weaponized exploit. The CVE is not marked KEV in the supplied bundle.

Researcher notes

The public evidence supports a NULL pointer dereference race in Linux md RCU handling. Missing data includes CVSS, CWE, exploitability, required privileges, and distribution-specific affected ranges. Avoid assuming impact beyond kernel panic without more vendor analysis.

Mitigation direction

  • Check kernel vendor advisories for CVE-2025-38621 applicability.
  • Update to a kernel containing the referenced stable fixes.
  • Prioritize hosts using md software RAID for storage availability.
  • Monitor for kernel oops or panic traces involving rdev_addable or md_start_sync.

Validation and detection

  • Inventory Linux kernel versions across production and recovery hosts.
  • Identify systems with md RAID configured or md modules loaded.
  • Confirm whether vendor kernels include the stable commits listed in the CVE.
  • Review crash logs for NULL dereferences in rdev_addable.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
3Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxbc08041b32abe6c9824f78735bac22018eabfc06, bc08041b32abe6c9824f78735bac22018eabfc06unaffected
LinuxLinux6.7, 0, 6.16.1, 6.17affected
Weakness

CWE details

No CWE listed

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