# CVE-2025-37756: net: tls: explicitly disallow disconnect

> A local attacker can trigger a kernel warning and potential instability by disconnecting a TLS socket, requiring a kernel patch to fix.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-37756, DEBIAN-CVE-2025-37756, GHSA-5cvr-qr2r-c7rm, ROOT-OS-DEBIAN-12-CVE-2025-37756, ROOT-OS-UBUNTU-2204-CVE-2025-37756, ROOT-OS-UBUNTU-2404-CVE-2025-37756, UBUNTU-CVE-2025-37756

## What is CVE-2025-37756?

CVE-2025-37756 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 1 May 2025. 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:

net: tls: explicitly disallow disconnect

syzbot discovered that it can disconnect a TLS socket and then
run into all sort of unexpected corner cases. I have a vague
recollection of Eric pointing this out to us a long time ago.
Supporting disconnect is really hard, for one thing if offload
is enabled we'd need to wait for all packets to be _acked_.
Disconnect is not commonly used, disallow it.

The immediate problem syzbot run into is the warning in the strp,
but that's just the easiest bug to trigger:

  WARNING: CPU: 0 PID: 5834 at net/tls/tls_strp.c:486 tls_strp_msg_load+0x72e/0xa80 net/tls/tls_strp.c:486
  RIP: 0010:tls_strp_msg_load+0x72e/0xa80 net/tls/tls_strp.c:486
  Call Trace:
   <TASK>
   tls_rx_rec_wait+0x280/0xa60 net/tls/tls_sw.c:1363
   tls_sw_recvmsg+0x85c/0x1c30 net/tls/tls_sw.c:2043
   inet6_recvmsg+0x2c9/0x730 net/ipv6/af_inet6.c:678
   sock_recvmsg_nosec net/socket.c:1023 [inline]
   sock_recvmsg+0x109/0x280 net/socket.c:1045
   __sys_recvfrom+0x202/0x380 net/socket.c:2237

## Which versions are affected by CVE-2025-37756?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37756?

Apply the vendor's patch.

## Is CVE-2025-37756 being exploited?

There is no known exploitation of CVE-2025-37756 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37756 and fix it if it is affected.

What it is: CVE-2025-37756 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 1 May 2025. 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-2025-37756 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2025-37756/ (Markdown: https://insights.sbomify.com/CVE-2025-37756/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37756
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37756
- OSV: https://osv.dev/vulnerability/CVE-2025-37756

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37756/
Summaries are generated and may contain mistakes; the official description above is the record.