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CVE-2026-99239

Bluetooth: L2CAP: refuse __l2cap_chan_add if chan already has conn

CVSS score

7.8

EPSS probability

—

Risk score

0.8

Published

3 h ago

OverviewPublic Exploits (0)NewsroomVulnerability Timeline
Patch status has not yet been verified

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Vulnerability description

DayBreach AI Explanation

Verified against sources

Linux Kernel Bluetooth L2CAP TOCTOU Vulnerability

Sources read

1

Source agreement

Tam uyum

Evidence confidence

%55

Short explanation

A TOCTOU (Time-of-Check to Time-of-Use) race condition vulnerability exists in the Linux kernel Bluetooth L2CAP subsystem during connection state handling.

Why does it matter?

This vulnerability allows a local attacker to corrupt sensitive memory structures and achieve high-impact security compromises on affected systems.

What should be done?

  • Follow vendor security advisories.
  • Apply kernel updates.
  • Review patching guidance to prevent exploitation.
Chain of evidence and sources2 verified claims

Linux çekirdeği Bluetooth L2CAP bileşeninde bir TOCTOU yarış durumu mevcuttur.

S0 · daybreach-canonicalS1 · cvelist

Zafiyet taban CVSS skoru 7.8 olarak değerlendirilmiştir.

S0 · daybreach-canonicalS1 · cvelist
Show the technical text from the sources

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: refuse __l2cap_chan_add if chan already has conn l2cap_chan may be linked to l2cap_conn at most once. This is assumed in several places, eg l2cap_chan_del cleanup. There is a TOCTOU race where the invariant is violated: [Task 1] [Task 2] l2cap_chan_connect l2cap_sock_bind l2cap_chan_lock lock_sock l2cap_state_change if (sk->sk_state != BT_OPEN) chan->state = BT_CONNECT l2cap_sock_state_change_cb chan->state = BT_BOUND sk->sk_state = BT_BOUND lock_sock <------------------ release_sock sk->sk_state = BT_CONNECT l2cap_sock_connect() does not check sk->sk_state, so since chan->state is now BT_BOUND, subsequent connect() ends up with second __l2cap_chan_add. Explicitly document and check the invariant in __l2cap_chan_add with WARN_ON_ONCE. The only callsite where it could be hit is l2cap_chan_connect, so add pre-check there to avoid relying on chan->state. chan->state read/write is not properly guarded currently so there can be other TOCTOUC problems. Add l2cap_lock_chan in l2cap_sock_bind() to guard chan->state write.

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

This explanation was compiled automatically from the source records. Scores, active exploitation, patch and exploit status come straight from the sources.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-99239 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1linuxLinux View
2linuxLinux View
Total affected vendors: 1|Products: 2

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
7.8CVSS V3_1HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVE CNA
7.8CVSS V31HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HNVD

Patch and Remediation Guide

Solution & Remediation Advisory

Patch status unknown

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Until a patch is confirmed, follow the vendor advisory; do not read an unknown status as “no patch”.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-99239 is associated with the following CWEs:

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')CWE-20: Improper Input Validation

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-99239 weaknesses.

CAPEC-66: SQL InjectionCAPEC-126: Path TraversalCAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureYerel erişim
PermissionsLow
UserGerekmiyor

Official Sources and Advisories

https://git.kernel.org/stable/c/85cc289eb08afa975375f838187369e68b429ee0vendor-advisoryhttps://git.kernel.org/stable/c/820579652b24ce277e0097cd65b42bd9b7b8bf07vendor-advisoryhttps://git.kernel.org/stable/c/e618d928ec7f88cbeadfa3542adcac40f474e629vendor-advisoryhttps://git.kernel.org/stable/c/fabaff1c59ff2cc89cb7e5bd0186a5e15f0c73b2vendor-advisoryhttps://git.kernel.org/stable/c/52fe88e4ef87311eee32b45c65603e7c69e75e7dvendor-advisoryhttps://git.kernel.org/stable/c/10c705dd706aa93164ba41f2566f15206d6c178evendor-advisoryhttps://git.kernel.org/stable/c/73820561d8cbfd3364a29b8fa77f1707f26029davendor-advisoryhttps://git.kernel.org/stable/c/d3afd7803f9bc2a8c4270199497b60158b2fc647vendor-advisory

CVSS Vector Radar Chart

7.8 / 10
Attack VectorLocalComplexityLowPrivilegesLowUser Interact.NoneConfidentialityLowIntegrityNoneAvailabilityHigh

Vulnerability Scoring Details

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack VectorLocal
Attack ComplexityLow
Privileges RequiredLow privileges
User InteractionNone required
Confidentiality (Gizlilik)Low
Integrity (Bütünlük)None
Availability (Erişilebilirlik)High

Yama durumu bilinmiyor

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CVE-2026-99239 · Bluetooth: L2CAP: refuse __l2cap_chan_add…