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CVE Record

CVE-2025-38453: io_uring/msg_ring: ensure io_kiocb freeing is deferred for RCU

In the Linux kernel, the following vulnerability has been resolved: io_uring/msg_ring: ensure io_kiocb freeing is deferred for RCU syzbot reports that defer/local task_work adding via msg_ring can hit a request that has been freed: CPU: 1 UID: 0 PID: 19356 Comm: iou-wrk-19354 Not tainted 6.16.0-rc4-syzkaller-00108-g17bbde2e1716 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: <TASK> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xd2/0x2b0 mm/kasan/report.c:521 kasan_report+0x118/0x150 mm/kasan/report.c:634 io_req_local_work_add io_uring/io_uring.c:1184 [inline] __io_req_task_work_add+0x589/0x950 io_uring/io_uring.c:1252 io_msg_remote_post io_uring/msg_ring.c:103 [inline] io_msg_data_remote io_uring/msg_ring.c:133 [inline] __io_msg_ring_data+0x820/0xaa0 io_uring/msg_ring.c:151 io_msg_ring_data io_uring/msg_ring.c:173 [inline] io_msg_ring+0x134/0xa00 io_uring/msg_ring.c:314 __io_issue_sqe+0x17e/0x4b0 io_uring/io_uring.c:1739 io_issue_sqe+0x165/0xfd0 io_uring/io_uring.c:1762 io_wq_submit_work+0x6e9/0xb90 io_uring/io_uring.c:1874 io_worker_handle_work+0x7cd/0x1180 io_uring/io-wq.c:642 io_wq_worker+0x42f/0xeb0 io_uring/io-wq.c:696 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> which is supposed to be safe with how requests are allocated. But msg ring requests alloc and free on their own, and hence must defer freeing to a sane time. Add an rcu_head and use kfree_rcu() in both spots where requests are freed. Only the one in io_msg_tw_complete() is strictly required as it has been visible on the other ring, but use it consistently in the other spot as well. This should not cause any other issues outside of KASAN rightfully complaining about it.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux io_uring memory-lifetime flaw can let a locally authenticated, low-privilege user trigger access to an already-freed request. The supplied CVSS assessment indicates possible compromise of confidentiality, integrity, and availability, although the source describes the observed failure through KASAN rather than a demonstrated real-world attack.

Executive priority

Treat as a high-priority kernel maintenance issue, especially on shared or multi-user Linux systems. It is not supported as an emergency internet-wide threat because exploitation requires local privileges and no active exploitation is documented. Obtain vendor package guidance promptly and schedule the corrected kernel according to local exposure.

Technical view

msg_ring requests can be freed while another ring still references them through deferred or local task work, creating a use-after-free condition. The kernel fix adds an rcu_head and uses kfree_rcu() at both request-freeing locations so reclamation occurs only after RCU readers are safe.

Likely exposure

Exposure is limited to Linux systems running the listed affected releases, including 6.11, 6.12.46, 6.15.7, and 6.16, where a low-privilege local account can reach the vulnerable io_uring msg_ring path. The supplied version data is unusual and insufficient for precise distribution-package mapping.

Exploitation context

The CVSS vector describes local, low-complexity exploitation requiring low privileges and no user interaction. The supplied record is not in KEV and provides no evidence of active exploitation, public weaponization, or remote reachability. Discovery came from syzbot with KASAN detecting the invalid memory access.

Researcher notes

The report identifies a request-lifetime race involving remote msg_ring posting and task-work addition. RCU-deferred freeing addresses visibility across rings. The source notes that only io_msg_tw_complete() strictly required the change, with the second free site updated for consistency. No exploitability demonstration or affected architecture constraints are supplied.

Mitigation direction

  • Install a vendor-supported kernel containing the referenced upstream fix or its distribution backport.
  • Check Linux distribution advisories for exact affected and corrected package versions.
  • Prioritize multi-user systems where untrusted local accounts can access io_uring.
  • Use vendor-recommended temporary restrictions if an immediate kernel update is unavailable.

Validation and detection

  • Record each host's running kernel release and distribution package version.
  • Map distribution packages to the three referenced stable-kernel fix commits.
  • Confirm the corrected kernel is installed and active after reboot.
  • Review whether untrusted local users can access the affected io_uring functionality.
Prepared
Confidence
medium
Sources
5

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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CVE-2025-38453 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

1CVSS vectors
3Timeline events
0ADP providers
4Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-38453Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux0617bb500bfabf8447062f1e1edde92ed2b638f1, 0617bb500bfabf8447062f1e1edde92ed2b638f1, 0617bb500bfabf8447062f1e1edde92ed2b638f1unaffected
LinuxLinux6.11, 0, 6.12.46, 6.15.7, 6.16affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.