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Linux KernelOperating system · Linux

CVE-2026-53256

HIGH · 8.0 CVSS v3.1 Published 2026-06-25
Fix available
A fix is available. Upgrade to 5.10.259 / 5.15.210 or later.
See remediation →
82/100
Remediation priority · High
Zero-click Patch available 8 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: Bluetooth: RFCOMM: hold listener socket in rfcomm_connect_ind() rfcomm_get_sock_by_channel() scans rfcomm_sk_list under the list lock, but returns the selected listener after dropping that lock without taking a reference. rfcomm_connect_ind() then locks the listener, queues a child socket on it, and may notify it after unlocking it. The buggy scenario involves two paths, with each column showing the order within that path: rfcomm_connect_ind(): listener close: 1. Find parent in 1. close() enters rfcomm_get_sock_by_channel() rfcomm_sock_release(). 2. Drop rfcomm_sk_list.lock 2. rfcomm_sock_shutdown() without pinning parent. closes the listener. 3. Call lock_sock(parent) and 3. rfcomm_sock_kill() bt_accept_enqueue(parent, unlinks and puts parent. sk, true). 4. Read parent flags and may 4. parent can be freed. call sk_state_change(). If close wins the race, parent can be freed before rfcomm_connect_ind() reaches lock_sock(), bt_accept_enqueue(), or the deferred-setup callback. Take a reference on the listener before leaving rfcomm_sk_list.lock. After lock_sock() succeeds, recheck that it is still in BT_LISTEN before queueing a child, cache the deferred-setup bit while the parent is locked, and drop the reference after the last parent use. KASAN reported a slab-use-after-free in lock_sock_nested() from rfcomm_connect_ind(), with the freeing stack going through rfcomm_sock_kill() and rfcomm_sock_release().

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 Linux kernel's Bluetooth RFCOMM implementation causes a use-after-free. The function rfcomm_get_sock_by_channel() returns a reference to a listener socket without taking a reference count, then drops the list lock. If another thread closes the listener socket during this window, the socket is freed, and the original code later attempts to use the freed memory in lock_sock(), bt_accept_enqueue(), or sk_state_change().

MitigationApply the kernel patch that adds proper reference counting: take a reference on the listener before dropping the list lock, recheck BT_LISTEN state after acquiring the lock, and drop the reference after final use. This is a kernel-level fix requiring code changes to rfcomm_connect_ind() and related functions.

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:>= 2.6.12.1, < 5.10.259>= 5.11, < 5.15.210>= 5.16, < 6.1.176>= 6.2, < 6.6.143>= 6.7, < 6.12.94>= 6.13, < 6.18.36>= 6.19, < 7.0.13= 2.6.12= 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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:L/PR:L/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. Identify the running Linux kernel version
    Run `uname -r` or check `/proc/version` to get the exact kernel version string
    Affected if The kernel version falls within any of the affected ranges: >= 2.6.12.1 and < 5.10.259; >= 5.11 and < 5.15.210; >= 5.16 and < 6.1.176; >= 6.2 and < 6.6.143; >= 6.7 and < 6.12.94; >= 6.13 and < 6.18.36; >= 6.19 and < 7.0.13; equals 2.6.12; or equals 7.1
  2. Verify if the Bluetooth subsystem is active
    Run `rfkill list` or check `hciconfig -a` to see if any Bluetooth adapters are present and powered on
    Affected if Bluetooth is enabled and active on the system, making the RFCOMM code path reachable
  3. Check if RFCOMM protocol is loaded or in use
    Run `lsmod | grep rfcomm` to check if the rfcomm kernel module is loaded, or check /proc/net/bluetooth/rfcomm for active connections
    Affected if The rfcomm module is loaded or there are active RFCOMM connections, indicating the vulnerable code path is exercised
  4. Inspect kernel configuration for RFCOMM support
    Check /boot/config-$(uname -r) or /proc/config.gz for CONFIG_BT_RFCOMM=m or =y
    Affected if RFCOMM support is compiled as a module (m) or built-in (y), making the vulnerability surface accessible

The system is affected if it runs a kernel version within the affected ranges AND has Bluetooth RFCOMM enabled or in use, allowing the race condition in rfcomm_get_sock_by_channel() to be triggered.

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.

dbcve · scoped
Upgrade available Upgrade to 5.10.259 / 5.15.210 / 6.1.176 or later
Fixed in 5.10.2595.15.2106.1.176
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that adds proper reference counting: take a reference on the listener before dropping the list lock, recheck BT_LISTEN state after acquiring the lock, and drop the reference after final use. This is a kernel-level fix requiring code changes to rfcomm_connect_ind() and related functions.

Recommended fix High confidence

Upgrade to kernel 5.10.259, 5.15.210, 6.1.176, or 6.6.143 (or later stable release) depending on which major version branch is in use

  1. Identify the current kernel version using 'uname -r' or 'cat /proc/version'
  2. Determine which affected version range applies (5.10.x, 5.15.x, 6.1.x, or 6.2.x through 6.6.x)
  3. For 5.10.x kernels: upgrade to version 5.10.259 or later
  4. For 5.11-5.15.x kernels: upgrade to version 5.15.210 or later
  5. For 5.16-6.1.x kernels: upgrade to version 6.1.176 or later
  6. For 6.2-6.6.x kernels: upgrade to version 6.6.143 or later
  7. Alternatively, apply the vendor patch commit 1f73f92f66251065a5f39b09a47cf05ea14d3107 to the kernel source and recompile
  8. Reboot into the patched or upgraded kernel
Caveat Kernel upgrades may require rebuilding out-of-tree modules; ensure compatible drivers and modules are available for the new kernel version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing5.0 h
  • Review / QA3.0 h
17.0 hours of engineering $2,970
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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-2026-53256 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
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  • Version or environment caveats, and links to real fixes
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