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VulnerabilityPublished Updated

CVE-2026-31772: Linux kernel · Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in f5d446624345d309e7a4a1b27ea9f028d6a8c5d9 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in f5d446624345d309e7a4a1b27ea9f028d6a8c5d9, eaf32002ca7b1ba51c9f140991fd9febe6de79f0, bc39a094730ce062fa034a529c93147c096cb488 +3
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=6.12.2 <6.12.81
  • >=6.11.11 <6.12
Fixed in
  • f5d446624345d309e7a4a1b27ea9f028d6a8c5d9
  • eaf32002ca7b1ba51c9f140991fd9febe6de79f0
  • bc39a094730ce062fa034a529c93147c096cb488
  • aba0aea354015794e8312dd7efe726967e58aefe
  • 6.12.81
  • 6.12
LinuxLinuxAffected
  • =6.13
Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync hci_le_big_create_sync() uses DEFINE_FLEX to allocate a struct hci_cp_le_big_create_sync on the stack with room for 0x11 (17) BIS entries. However, conn->num_bis can hold up to HCI_MAX_ISO_BIS (31) entries — validated against ISO_MAX_NUM_BIS (0x1f) in the caller hci_conn_big_create_sync(). When conn->num_bis is between 18 and 31, the memcpy that copies conn->bis into cp->bis writes up to 14 bytes past the stack buffer, corrupting adjacent stack memory. This is trivially reproducible: binding an ISO socket with bc_num_bis = ISO_MAX_NUM_BIS (31) and calling listen() will eventually trigger hci_le_big_create_sync() from the HCI command sync worker, causing a KASAN-detectable stack-out-of-bounds write: BUG: KASAN: stack-out-of-bounds in hci_le_big_create_sync+0x256/0x3b0 Write of size 31 at addr ffffc90000487b48 by task kworker/u9:0/71 Fix this by changing the DEFINE_FLEX count from the incorrect 0x11 to HCI_MAX_ISO_BIS, which matches the maximum number of BIS entries that conn->bis can actually carry.

References

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