CVE-2026-63975
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 · uneditedIn the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix possible crash on l2cap_ecred_conn_rsp If dcid is received for an already-assigned destination CID the spec requires that both channels to be discarded, but calling l2cap_chan_del may invalidate the tmp cursor created by list_for_each_entry_safe and in fact it is the wrong procedure as the chan->dcid may be assigned previously it really needs to be disconnected. Calling l2cap_chan_clone directly may still lead to l2cap_chan_del so instead schedule l2cap_chan_timeout with delay 0 to close the channel asynchronously.
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 confidenceA crash occurs in l2cap_ecred_conn_rsp when processing a destination CID (dcid) for an already-assigned channel. The l2cap_chan_del function invalidates the list iterator used by list_for_each_entry_safe, causing a use-after-free or crash. The fix replaces direct channel deletion with scheduling l2cap_chan_timeout with delay 0 for asynchronous channel closure.
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 checksWork through these to decide whether this CVE applies to you.
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Check kernel versionRun `uname -r` to get the running kernel version. Compare it to the version that includes the fix for this CVE (typically kernel 6.x.y where y is after the patch date, or check your distribution's security advisories)Affected if Running a kernel version older than the patched version that contains the l2cap ECRED fix
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Verify Bluetooth kernel module is loadedRun `lsmod | grep bluetooth` or `modinfo bluetooth` to check if the Bluetooth core module is loadedAffected if Bluetooth module is loaded - the vulnerability exists in the L2CAP Bluetooth subystem
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Check if L2CAP protocol is activeRun `rfcomm -a` or check /proc/bluetooth/ for active L2CAP channels. Also check `hciconfig -a` to see if any Bluetooth adapters are upAffected if Any Bluetooth adapter is up and L2CAP connections are in use - the vulnerable code path is exercised when ECRED connection responses are processed
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Confirm ECRED connection handling is in useL2CAP ECRED (Enhanced Credit Based) is used for Bluetooth LE connections. Check active connections via `btmon` log or check /sys/kernel/debug/bluetooth/hci* for connection detailsAffected if Bluetooth LE or Classic connections using L2CAP ECRED are active - the specific code path handling ECRED connection responses is triggered
A system is affected if it runs a vulnerable Linux kernel version AND has Bluetooth enabled with L2CAP ECRED connections in use, as the crash occurs when processing an already-assigned destination CID in the ECRED connection response handler.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the Linux kernel patch that modifies l2cap_ecred_conn_rsp to schedule asynchronous channel closure via l2cap_chan_timeout instead of calling l2cap_chan_del directly.
- Consultation1.0 h
- Implementation3.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-63975 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-63975 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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