# CVE-2026-74282: tipc: prevent snt_unacked underflow on CONN_ACK

> A remote attacker can cause a denial of service in the Linux kernel TIPC protocol by sending a crafted connection acknowledgment that triggers an integer underflow.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74282, DEBIAN-CVE-2026-74282, GHSA-5xv7-x5qx-3wv4, UBUNTU-CVE-2026-74282

## What is CVE-2026-74282?

CVE-2026-74282 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

tipc: prevent snt_unacked underflow on CONN_ACK

tipc_sk_conn_proto_rcv() subtracts the peer-supplied connection ack count
from the unsigned 16-bit send counter snt_unacked without checking that it
does not exceed the number of messages actually outstanding:

	tsk->snt_unacked -= msg_conn_ack(hdr);

msg_conn_ack() is read straight from a received CONN_MANAGER/CONN_ACK
message. If the ack count is larger than snt_unacked, the subtraction
wraps to a near-maximum value, leaving tsk_conn_cong() permanently true
and starving the connection of further transmits.

Validate the ACK count at the start of the CONN_ACK block and drop the
message if it acknowledges more messages than are outstanding. A peer (or,
for a local connection, the connected peer socket) can otherwise wedge a
TIPC connection's send side by sending an oversized connection ack.

## Which versions are affected by CVE-2026-74282?


## How do I fix CVE-2026-74282?

Apply the vendor's patch.

## Is CVE-2026-74282 being exploited?

There is no known exploitation of CVE-2026-74282 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74282 and fix it if it is affected.

What it is: CVE-2026-74282 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74282 in the wild and no public exploit code.

Affected product: 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-2026-74282/ (Markdown: https://insights.sbomify.com/CVE-2026-74282/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74282
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74282
- OSV: https://osv.dev/vulnerability/CVE-2026-74282

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74282/
Summaries are generated and may contain mistakes; the official description above is the record.