CVE-2025-39773

Service hang via bridge timer overflow

Published Sep 11, 2025 · Updated Sep 11, 2025

Integer overflow in Linux kernel 2.6.34 and later allows local users to cause a soft lockup through bridge multicast settings. br_multicast_send_query() stores an oversized multicast query interval in a narrower time variable, producing an expired timer that mod_timer() repeatedly rearms. The trigger requires local bridge-configuration privileges; the resulting timer loop can monopolize a CPU and interrupt service.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Linux kernel 2.6.34 and later allows local users to cause a soft lockup through bridge multicast settings. br_multicast_send_query() stores an oversized multicast query interval in a narrower time variable, producing an expired timer that mod_timer() repeatedly rearms. The trigger requires local bridge-configuration privileges; the resulting timer loop can monopolize a CPU and interrupt service.

The record

CVE
CVE-2025-39773
Published
Sep 11, 2025
Updated
Sep 11, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-667, T1499
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=2.6.34
  2. Affected versionversion=d902eee43f1951b358d7347d9165c6af21cf7b1b <34171b9e53bd1dc264f5556579f2b04f04435c73
  3. Affected versionversion=d902eee43f1951b358d7347d9165c6af21cf7b1b <43e281fde5e76a866a4d10780c35023f16c0e432
  4. Affected versionversion=d902eee43f1951b358d7347d9165c6af21cf7b1b <5bf5fce8a0c2a70d063af778fdb5b27238174cdd
  5. Affected versionversion=d902eee43f1951b358d7347d9165c6af21cf7b1b <96476b043efb86a94f2badd260f7f99c97bd5893
  6. Affected versionversion=d902eee43f1951b358d7347d9165c6af21cf7b1b <bdb19cd0de739870bb3494c815138b9dc30875c4
  7. Affected versionversion=d902eee43f1951b358d7347d9165c6af21cf7b1b <d1547bf460baec718b3398365f8de33d25c5f36f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.34; version=d902eee43f1951b358d7347d9165c6af21cf7b1b <34171b9e53bd1dc264f5556579f2b04f04435c73; version=d902eee43f1951b358d7347d9165c6af21cf7b1b <43e281fde5e76a866a4d10780c35023f16c0e432; version=d902eee43f1951b358d7347d9165c6af21cf7b1b <5bf5fce8a0c2a70d063af778fdb5b27238174cdd; version=d902eee43f1951b358d7347d9165c6af21cf7b1b <96476b043efb86a94f2badd260f7f99c97bd5893; version=d902eee43f1951b358d7347d9165c6af21cf7b1b <bdb19cd0de739870bb3494c815138b9dc30875c4; version=d902eee43f1951b358d7347d9165c6af21cf7b1b <d1547bf460baec718b3398365f8de33d25c5f36f

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-667Improper Locking
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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