CVE-2025-39749

Local unspecified impact via RCU flag race

Published Sep 11, 2025 · Updated Sep 11, 2025

A data race in the Linux RCU subsystem allows local users to trigger unspecified impact during deferred quiescent-state handling. The rcu_preempt_deferred_qs_handler function updates the per-CPU defer_qs_iw_pending flag with interrupts enabled, so an interrupt-side rcu_read_unlock_special access can race with it. Reachability requires CONFIG_IRQ_WORK and the relevant nested interrupt and RCU sequence; the upstream record reports a KCSAN race but no concrete operational consequence.

CVSS severity7.0
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A data race in the Linux RCU subsystem allows local users to trigger unspecified impact during deferred quiescent-state handling. The rcu_preempt_deferred_qs_handler function updates the per-CPU defer_qs_iw_pending flag with interrupts enabled, so an interrupt-side rcu_read_unlock_special access can race with it. Reachability requires CONFIG_IRQ_WORK and the relevant nested interrupt and RCU sequence; the upstream record reports a KCSAN race but no concrete operational consequence.

The record

CVE
CVE-2025-39749
Published
Sep 11, 2025
Updated
Sep 11, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0ad84d62217488e679ecc90e8628980dcc003de3
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <55e11f6776798b27cf09a7aa0d718415d4fc9cf5
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <74f58f382a7c8333f8d09701aefaa25913bdbe0e
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <90c09d57caeca94e6f3f87c49e96a91edd40cbfd
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <90de9c94ea72327cfa9c2c9f6113c23a513af60b
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b55947b725f190396f475d5d0c59aa855a4d8895
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b5de8d80b5d049f051b95d9b1ee50ae4ab656124
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e35e711c78c8a4c43330c0dcb1c4d507a19c20f4
  9. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f937759c7432d6151b73e1393b6517661813d506

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0ad84d62217488e679ecc90e8628980dcc003de3; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <55e11f6776798b27cf09a7aa0d718415d4fc9cf5; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <74f58f382a7c8333f8d09701aefaa25913bdbe0e; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <90c09d57caeca94e6f3f87c49e96a91edd40cbfd; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <90de9c94ea72327cfa9c2c9f6113c23a513af60b; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b55947b725f190396f475d5d0c59aa855a4d8895; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b5de8d80b5d049f051b95d9b1ee50ae4ab656124; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e35e711c78c8a4c43330c0dcb1c4d507a19c20f4; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f937759c7432d6151b73e1393b6517661813d506

Published CVSS scores

7.0UbuntuCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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