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ZephyrOperating system · Zephyrproject

CVE-2026-10680

HIGH · 7.6 CVSS v3.1 Developing Published 2026-07-21
Fix available
A fix is available. Upgrade to 4.3.1 or later.
See remediation →
81/100
Remediation priority · High
No privileges Zero-click 4 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
The Classic (BR/EDR) L2CAP signaling handlers l2cap_br_conf_req() and l2cap_br_conf_rsp() in subsys/bluetooth/host/classic/l2cap_br.c validated the minimum command size against buf->len (the bytes remaining in the whole received PDU) instead of len (the per-command data length from the L2CAP signaling header). Because multiple signaling commands can be packed into one PDU, buf->len may exceed a command's len. An attacker can send a CONF_REQ command with a header length smaller than the configuration-request structure (e.g. 0), followed by another command so that buf->len still satisfies the check. The check then passes incorrectly and opt_len = len - sizeof(*req) underflows the uint16_t to a near-0xFFFF value. The configuration-option loop, which lacks an opt_len-versus-buf->len guard, then walks far past the end of the pooled ACL receive buffer using net_buf pull primitives that perform no runtime bounds check, producing an out-of-bounds read of host memory and, when the out-of-bounds option bytes encode an MTU or flush-timeout option, an out-of-bounds write. The BR/EDR signaling channel is processed before pairing/encryption and an L2CAP channel to an L0 service such as SDP can be opened without pairing, so an unauthenticated peer within radio range that can establish an ACL connection can trigger the flaw, leading to memory corruption and denial of service (host/device crash). The defect is present in released versions including v4.4.0. The fix validates against len instead of buf->len in both handlers.

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 · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-04.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
ZephyrOperating system
Affected:>= 4.2.0, < 4.3.1>= 4.4.0, <= 4.4.1

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
Low
Integrity
Low
Availability
High

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

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.

dbcve · scoped
Upgrade available Upgrade to 4.3.1 or later
Fixed in 4.3.1
Recommended fix Moderate confidence

Latest stable Zephyr RTOS release after v4.4.0 (e.g., v4.5.0 or later stable branch)

  1. 1. Identify the current Zephyr RTOS version in use by checking the manifest file (west.yml) or the VERSION file in the project
  2. 2. Navigate to the Zephyr GitHub repository releases page: https://github.com/zephyrproject-rtos/zephyr/releases
  3. 3. Identify the latest stable release version that includes the security fix for CVE-2026-10680 (versions after v4.4.0)
  4. 4. Update the west.yml manifest to point to the fixed version, or clone the specific tag/branch containing the fix
  5. 5. Rebuild the Bluetooth host stack and flash the updated firmware to the device
  6. 6. Verify the fix by reviewing the patched l2cap_br.c file, ensuring the validation now uses 'len' instead of 'buf->len' in both l2cap_br_conf_req() and l2cap_br_conf_rsp() functions
Caveat Minor: The fix changes validation logic; ensure any custom L2CAP configuration handling is compatible with correct per-command length validation

Generated from the published advisory — verify against the referenced sources before acting.

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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

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Peer-ranked notes from engineers who’ve handled CVE-2026-10680 in production — separate from our analysis above.

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