VulnerabilityPublished 27 Jul 2026Updated 17 Aug 2026

CVE-2026-64537: Linux kernel · bridge: cfm: reject invalid CCM interval at configuration time

Affects Linux kernelSource GCVE Database

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Not known to be exploited.

Data as of 3 Nov 2026, 18:43 UTC

Severity

High

Rated High by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

A fix is available that validates the CCM interval at configuration time to ensure it is within the valid range and rejects invalid or unconfigured intervals. Users should apply the official Linux kernel update that includes this validation to prevent exploitation.

Description

A vulnerability in the Linux kernel bridge component's Connectivity Fault Management (CFM) feature allows invalid Continuity Check Message (CCM) intervals to be set at configuration time. This can cause a worker function to enter a tight loop allocating memory until the system runs out of memory (OOM). The issue is fixed by validating the CCM interval during configuration to ensure it falls within a valid range and rejecting invalid or unconfigured intervals.

Impact

An attacker or misconfigured userspace process could cause the kernel to enter a tight loop allocating memory, potentially leading to system instability or denial of service due to out-of-memory conditions.

Summary

The Linux kernel's bridge CFM implementation had a flaw where the CCM transmit worker function (ccm_tx_work_expired) re-armed itself using a configured interval converted to microseconds. If the configured exp_interval was set to BR_CFM_CCM_INTERVAL_NONE or an out-of-range value, the conversion returned zero, causing the worker to execute immediately in a tight loop that continuously allocated socket buffers (skbs) until the system exhausted memory. The fix involves validating the exp_interval at configuration time by constraining it within the valid range [BR_CFM_CCM_INTERVAL_3_3_MS, BR_CFM_CCM_INTERVAL_10_MIN] in the netlink policy, preventing userspace from setting invalid values, and rejecting CCM TX start if the interval is unconfigured.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 3 Nov 2026, 18:43 UTC

Technical details

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