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Linux KernelOperating system · Linux

CVE-2026-64093

HIGH · 8.8 CVSS v3.1 Published 2026-07-19
Fix available
A fix is available. Upgrade to 5.15.210 / 6.1.176 or later.
See remediation →
93/100
Remediation priority · Urgent
No privileges Zero-click 4 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: batman-adv: tp_meter: directly shut down timer on cleanup batadv_tp_sender_cleanup() was calling timer_delete_sync() followed by timer_delete() to guard against the timer handler re-arming itself between the two calls. This double-deletion hack relied on the sending status being set to 0 to suppress re-arming. Replace both calls with a single timer_shutdown_sync(). This function both waits for any running timer callback to complete (like timer_delete_sync()) and permanently disarms the timer so it cannot be re-armed afterwards, making re-arming prevention unconditional and self-documenting. The re-arming property is also required because otherwise: 1. context 0 (batadv_tp_recv_ack()) checks in batadv_tp_reset_sender_timer() if sending is still 1 -> it is 2. context 1 changes in batadv_tp_sender_shutdown() sending to 0 and in this process forces the kthread to stop timer in batadv_tp_sender_cleanup() 3. context 0 continues in batadv_tp_reset_sender_timer() and rearms the timer -> but the reference for it is already gone

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition in batman-adv's tp_meter timer handling allowed timer re-arming after cleanup references were removed. The old code used a flawed double-deletion pattern (timer_delete_sync() + timer_delete()) relying on a status flag to prevent re-arm, but context 0 could re-arm the timer in batadv_tp_reset_sender_timer() after context 1 had already cleared the reference in batadv_tp_sender_cleanup(), potentially causing use-after-free or null pointer dereference.

MitigationUpdate the Linux kernel to a version containing the fix that replaces the flawed double-deletion pattern with timer_shutdown_sync(), which unconditionally prevents timer re-arming while waiting for any running callbacks.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.8, < 5.15.210>= 5.16, < 6.1.176>= 6.2, < 6.6.143>= 6.7, < 6.12.93>= 6.13, < 6.18.34>= 6.19, < 7.0.11= 7.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if batman-adv kernel module is loaded
    Run 'lsmod | grep batman_adv' or check /sys/module/batman_adv/
    Affected if The module is not loaded, the vulnerability does not apply to this system
  2. Check if batctl userspace tool is installed
    Run 'which batctl' or 'dpkg -l batctl'
    Affected if Without batctl, tp_meter cannot be initiated, reducing but not eliminating risk (kernel module could still have the flaw)
  3. Identify active tp_meter sessions
    Run 'batctl tp_meter -l' or check /sys/kernel/debug/batman_adv/ for throughput meter status
    Affected if Active or recent tp_meter sessions indicate the vulnerable code path was exercised
  4. Determine kernel version and compare to fix date
    Run 'uname -r' to get kernel version, then research when the fix (timer_shutdown_sync replacement) was merged
    Affected if Running a kernel released before the fix date means the vulnerability is present
  5. Inspect batman-adv source for vulnerable pattern
    Check if the source file net/batman-adv/tp_meter.c contains the flawed timer_delete_sync() then timer_delete() pattern
    Affected if The flawed double timer deletion pattern exists, indicating the vulnerability is present

A system is affected if it loads the batman-adv module, runs a kernel predating the fix, and has the vulnerable timer deletion pattern in the tp_meter component code.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 5.15.210 / 6.1.176 / 6.6.143 or later
Fixed in 5.15.2106.1.1766.6.143
Interim mitigation

Update the Linux kernel to a version containing the fix that replaces the flawed double-deletion pattern with timer_shutdown_sync(), which unconditionally prevents timer re-arming while waiting for any running callbacks.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-64093 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data