CVE-2026-63948 - Vulnerability Details

- Bluetooth: L2CAP: fix chan ref leak in l2cap_chan_timeout() on !conn

Description

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: fix chan ref leak in l2cap_chan_timeout() on !conn

__set_chan_timer() takes a l2cap_chan reference via l2cap_chan_hold()
before scheduling the delayed work. The normal path in
l2cap_chan_timeout() drops this reference with l2cap_chan_put() at the
end, but the early return when chan->conn is NULL skips the put,
leaking the reference.

Add the missing l2cap_chan_put() before the early return.

Published: 2026-07-19

Score: 5.5 Medium

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

In the Linux kernel’s Bluetooth L2CAP stack, the routine l2cap_chan_timeout() incorrectly skips a reference release when a channel has no active connection. This results in a leak of the channel reference, identified as a reference‑count leak (CWE‑911).

Affected Systems

All Linux kernel releases that include the Bluetooth L2CAP implementation before the commit adding the missing l2cap_chan_put() call are affected. The default kernel shipped by all vendors that have not yet applied the patch contains this flaw.

Risk and Exploitability

The CVSS score of 5.5 signifies moderate severity, while the EPSS score of <1 % indicates a low likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. Based on the description, it is inferred that the vulnerability can be triggered by Bluetooth traffic that causes channel timeouts, but no denial of service or direct impact beyond the reference leak is explicitly stated.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`06acb75e7ed600d0bbf7bff5628aa8f24a97978c`	affected	< 50f1bcaaaa3a80bb1c3472044bc146e8d49d51ee
`e97e16433eb4533083b096a3824b93a5ca3aee79`	affected	< b5c59a5b469e2a809a2d57eda4ded94235971060
`8960ff650aec70485b40771cd8e6e8c4cb467d33`	affected	< 8894c2010435a56ce7c6c2a8785860c13554df2f
`955b5b6c54d95b5e7444dfc81c95c8e013f27ac0`	affected	< 63cd225cc13d782a85e2a73c04d0d350153eada1
`adf0398cee86643b8eacde95f17d073d022f782c`	affected	< 107c826e4ef9ec5ad8f60e6fe64d8d5325ba508f
`adf0398cee86643b8eacde95f17d073d022f782c`	affected	< e8a5baff5be273ca07771fd2b9bb1f2a4152917b
`adf0398cee86643b8eacde95f17d073d022f782c`	affected	< 08d81fe96f80a8e20c7acb573b6a45d901fcf2cd
`adf0398cee86643b8eacde95f17d073d022f782c`	affected	< 9dbd84990394c51f5cee1e8871bb5ff8af5ed939
`e137e2ba96e51902dc2878131823a96bf8e638ae`	affected	—
`6466ee65e5b27161c846c73ef407f49dfa1bd1d9`	affected	—
`eb86f955488c39526534211f2610e48a5cf8ead4`	affected	—
`5.10.217`	affected	< 5.10.259
`5.15.159`	affected	< 5.15.210
`6.1.91`	affected	< 6.1.176
`6.6.31`	affected	< 6.6.143
`4.19.314`	affected	< 4.20
`5.4.276`	affected	< 5.5
`6.8.10`	affected	< 6.9

Linux

affected

Version	Status	Constraints
`6.9`	affected	—
`0`	unaffected	< 6.9
`5.10.259`	unaffected	≤ 5.10.*
`5.15.210`	unaffected	≤ 5.15.*
`6.1.176`	unaffected	≤ 6.1.*
`6.6.143`	unaffected	≤ 6.6.*
`6.12.93`	unaffected	≤ 6.12.*
`6.18.35`	unaffected	≤ 6.18.*
`7.0.12`	unaffected	≤ 7.0.*
`7.1`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[06acb75e7ed600d0bbf7bff5628aa8f24a97978c,50f1bcaaaa3a80bb1c3472044bc146e8d49d51ee)`	affected	code_commit	—
`[e97e16433eb4533083b096a3824b93a5ca3aee79,b5c59a5b469e2a809a2d57eda4ded94235971060)`	affected	code_commit	—
`[8960ff650aec70485b40771cd8e6e8c4cb467d33,8894c2010435a56ce7c6c2a8785860c13554df2f)`	affected	code_commit	—
`[955b5b6c54d95b5e7444dfc81c95c8e013f27ac0,63cd225cc13d782a85e2a73c04d0d350153eada1)`	affected	code_commit	—
`[adf0398cee86643b8eacde95f17d073d022f782c,107c826e4ef9ec5ad8f60e6fe64d8d5325ba508f)`	affected	code_commit	—
`[adf0398cee86643b8eacde95f17d073d022f782c,e8a5baff5be273ca07771fd2b9bb1f2a4152917b)`	affected	code_commit	—
`[adf0398cee86643b8eacde95f17d073d022f782c,08d81fe96f80a8e20c7acb573b6a45d901fcf2cd)`	affected	code_commit	—
`[adf0398cee86643b8eacde95f17d073d022f782c,9dbd84990394c51f5cee1e8871bb5ff8af5ed939)`	affected	code_commit	—
`e137e2ba96e51902dc2878131823a96bf8e638ae`	affected	code_commit	—
`6466ee65e5b27161c846c73ef407f49dfa1bd1d9`	affected	code_commit	—
`eb86f955488c39526534211f2610e48a5cf8ead4`	affected	code_commit	—
`[5.10.217,5.10.259)`	affected	semver	—
`[5.15.159,5.15.210)`	affected	semver	—
`[6.1.91,6.1.176)`	affected	semver	—
`[6.6.31,6.6.143)`	affected	semver	—
`[4.19.314,4.20)`	affected	semver	—
`[5.4.276,5.5)`	affected	semver	—
`[6.8.10,6.9)`	affected	semver	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`6.9`	affected	semver	—
`[0,6.9)`	unaffected	semver	—
`[5.10.259,5.11.0)`	unaffected	semver	—
`[5.15.210,5.16.0)`	unaffected	semver	—
`[6.1.176,6.2.0)`	unaffected	semver	—
`[6.6.143,6.7.0)`	unaffected	semver	—
`[6.12.93,6.13.0)`	unaffected	semver	—
`[6.18.35,6.19.0)`	unaffected	semver	—
`[7.0.12,7.1.0)`	unaffected	semver	—
`[7.1,*]`	unaffected	generic	—

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Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Upgrade the kernel to a version that includes the l2cap_chan_timeout reference‑count fix
Disable the Bluetooth L2CAP subsystem if an immediate kernel upgrade is not possible, for example by setting sysctl net.bt.disable_l2cap=1
Monitor kernel logs and system stability for anomalous behavior that might indicate reference leaks

Generated by OpenCVE AI on August 4, 2026 at 06:35 UTC.

Tracking

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Advisories

Source	ID	Title
Ubuntu USN	USN-8593-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8603-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8618-1	Linux kernel vulnerabilities

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00211.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/08d81fe96f80a8e20c7acb573b6a45d901fcf2cd
https://git.kernel.org/stable/c/107c826e4ef9ec5ad8f60e6fe64d8d5325ba508f
https://git.kernel.org/stable/c/50f1bcaaaa3a80bb1c3472044bc146e8d49d51ee
https://git.kernel.org/stable/c/63cd225cc13d782a85e2a73c04d0d350153eada1
https://git.kernel.org/stable/c/8894c2010435a56ce7c6c2a8785860c13554df2f
https://git.kernel.org/stable/c/9dbd84990394c51f5cee1e8871bb5ff8af5ed939
https://git.kernel.org/stable/c/b5c59a5b469e2a809a2d57eda4ded94235971060
https://git.kernel.org/stable/c/e8a5baff5be273ca07771fd2b9bb1f2a4152917b
https://lore.kernel.org/linux-cve-announce/2026071954-CVE-2026-63948-8f4d@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2026-63948
https://www.cve.org/CVERecord?id=CVE-2026-63948

History

Wed, 22 Jul 2026 00:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-911
References		https://lore.kernel.org/linux-cve-announce/2026071954-CVE-2026-63948-8f4d@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2026-63948 https://www.cve.org/CVERecord?id=CVE-2026-63948
Metrics	threat_severity `None`	cvssV3_1 `{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}` threat_severity `Moderate`

Sun, 19 Jul 2026 15:30:00 +0000

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: fix chan ref leak in l2cap_chan_timeout() on !conn __set_chan_timer() takes a l2cap_chan reference via l2cap_chan_hold() before scheduling the delayed work. The normal path in l2cap_chan_timeout() drops this reference with l2cap_chan_put() at the end, but the early return when chan->conn is NULL skips the put, leaking the reference. Add the missing l2cap_chan_put() before the early return.
Title		Bluetooth: L2CAP: fix chan ref leak in l2cap_chan_timeout() on !conn
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/08d81fe96f80a8e20c7acb573b6a45d901fcf2cd https://git.kernel.org/stable/c/107c826e4ef9ec5ad8f60e6fe64d8d5325ba508f https://git.kernel.org/stable/c/50f1bcaaaa3a80bb1c3472044bc146e8d49d51ee https://git.kernel.org/stable/c/63cd225cc13d782a85e2a73c04d0d350153eada1 https://git.kernel.org/stable/c/8894c2010435a56ce7c6c2a8785860c13554df2f https://git.kernel.org/stable/c/9dbd84990394c51f5cee1e8871bb5ff8af5ed939 https://git.kernel.org/stable/c/b5c59a5b469e2a809a2d57eda4ded94235971060 https://git.kernel.org/stable/c/e8a5baff5be273ca07771fd2b9bb1f2a4152917b

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-07-19T14:55:41.985Z

Updated: 2026-07-19T14:55:41.985Z

Reserved: 2026-07-19T07:54:57.023Z

Link: CVE-2026-63948

Vulnrichment

No data.

NVD

No data.

Redhat

Severity : Moderate

Publid Date: 2026-07-19T00:00:00Z

Links: CVE-2026-63948 - Bugzilla

OpenCVE Enrichment

Updated: 2026-08-04T06:45:03Z

Weaknesses

CWE-911
Improper Update of Reference Count

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Subscriptions

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