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VulnerabilityAwaiting classification

CVE-2026-63946

HIGH · 8.8 CVSS v3.1 Published 2026-07-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
93/100
Remediation priority · Urgent
No privileges Zero-click 5 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: ISO: fix UAF in iso_recv_frame iso_recv_frame reads conn->sk under iso_conn_lock but releases the lock before using sk, with no reference held. A concurrent iso_sock_kill() can free sk in that window, causing use-after-free on sk->sk_state and sock_queue_rcv_skb(). Fix by replacing the bare pointer read with iso_sock_hold(conn), which calls sock_hold() while the spinlock is held, atomically elevating the refcount before the lock drops. Add a drop_put label so sock_put() is called on all exit paths where the hold succeeded.

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 use-after-free vulnerability exists in the Linux kernel's Bluetooth ISO subsystem where iso_recv_frame reads the socket pointer under a spinlock but releases the lock before using the socket, creating a window where concurrent iso_sock_kill() can free the socket. The fix involves using iso_sock_hold() to atomically increment the socket reference count while holding the lock, ensuring the socket remains valid.

MitigationApply the kernel patch that replaces the bare conn->sk pointer read with iso_sock_hold() to properly hold a reference, and ensure all code paths call sock_put() via the new drop_put label.

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

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 kernel version against fixed release
    Run `uname -r` to get the running kernel version. Compare against the kernel version that contains the fix for this vulnerability (Linux kernel mainline after the fix commit).
    Affected if Kernel version is older than the fixed version and the Bluetooth ISO subsystem is in use.
  2. Verify Bluetooth ISO support is active
    Check if the kernel has Bluetooth ISO support enabled by running `lsmod | grep -i iso` or checking `cat /proc/kallsyms | grep iso_recv_frame`. Also check kernel config with `zcat /proc/config.gz 2>/dev/null | grep -i ISO` or check /boot/config-$(uname -r)
    Affected if The iso_recv_frame function is present and the btiso kernel module or Bluetooth ISO functionality is loaded/available.
  3. Confirm iso_sock_hold is missing (vulnerable code present)
    Check the kernel symbol table or source for the iso_recv_frame function. Run `nm /lib/modules/$(uname -r)/kernel/net/bluetooth/iso.ko 2>/dev/null | grep iso_sock_hold` or inspect the compiled code for the presence of iso_sock_hold calls around the sk pointer access.
    Affected if The iso_recv_frame function does NOT use iso_sock_hold() before accessing sk->sk_state, indicating the vulnerable code pattern exists.
  4. Check for active ISO connections
    Monitor for active Bluetooth ISO connections using `btmon` or check /sys/kernel/debug/bluetooth/iso* for existing connections. Also check `cat /proc/net/bluetooth/iso` if available.
    Affected if Active ISO connections exist, which would trigger the vulnerable code path in iso_recv_frame.

The environment is affected if running a vulnerable Linux kernel version (pre-fix) with Bluetooth ISO support enabled and active ISO connections present, as the UAF window exists when iso_recv_frame accesses the socket pointer outside the spinlock.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the kernel patch that replaces the bare conn->sk pointer read with iso_sock_hold() to properly hold a reference, and ensure all code paths call sock_put() via the new drop_put label.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,580
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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-2026-63946 in production — separate from our analysis above.

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What this is

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What belongs here
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