# CVE-2026-31393: Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access

> A missing length check in the Linux kernel Bluetooth L2CAP handler allows attackers to read out-of-bounds memory via a truncated response.

- **Severity:** High 8.1 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Apr 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-31393, DEBIAN-CVE-2026-31393, GHSA-cpmg-r9cr-q8pj, ROOT-OS-DEBIAN-11-CVE-2026-31393, ROOT-OS-DEBIAN-12-CVE-2026-31393, ROOT-OS-DEBIAN-13-CVE-2026-31393, ROOT-OS-UBUNTU-2204-CVE-2026-31393, ROOT-OS-UBUNTU-2404-CVE-2026-31393, UBUNTU-CVE-2026-31393

## What is CVE-2026-31393?

CVE-2026-31393 is a high-severity vulnerability in Linux kernel, published on 3 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access

l2cap_information_rsp() checks that cmd_len covers the fixed
l2cap_info_rsp header (type + result, 4 bytes) but then reads
rsp->data without verifying that the payload is present:

 - L2CAP_IT_FEAT_MASK calls get_unaligned_le32(rsp->data), which reads
   4 bytes past the header (needs cmd_len >= 8).

 - L2CAP_IT_FIXED_CHAN reads rsp->data[0], 1 byte past the header
   (needs cmd_len >= 5).

A truncated L2CAP_INFO_RSP with result == L2CAP_IR_SUCCESS triggers an
out-of-bounds read of adjacent skb data.

Guard each data access with the required payload length check.  If the
payload is too short, skip the read and let the state machine complete
with safe defaults (feat_mask and remote_fixed_chan remain zero from
kzalloc), so the info timer cleanup and l2cap_conn_start() still run
and the connection is not stalled.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-31393?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31393?

Apply the vendor's patch.

## Is CVE-2026-31393 being exploited?

There is no known exploitation of CVE-2026-31393 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31393 and fix it if it is affected.

What it is: CVE-2026-31393 is a high-severity vulnerability in Linux kernel, published on 3 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31393 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31393/ (Markdown: https://insights.sbomify.com/CVE-2026-31393/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31393
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31393
- OSV: https://osv.dev/vulnerability/CVE-2026-31393

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31393/
Summaries are generated and may contain mistakes; the official description above is the record.