# CVE-2026-98805: tipc: prevent GCM nonce reuse on peer key changes

> An attacker on the network can decrypt and forge TIPC traffic due to nonce reuse when peer keys change, compromising confidentiality and integrity.

- **Severity:** Not scored
- **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:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-108590, BELL-CVE-2026-98805, DEBIAN-CVE-2026-98805, GHSA-c3cw-v3mg-q5gm, UBUNTU-CVE-2026-98805

## What is CVE-2026-98805?

CVE-2026-98805 is a vulnerability in Linux, published on 18 Oct 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:

tipc: prevent GCM nonce reuse on peer key changes

TIPC can encrypt traffic between nodes using a different transmit key
for each node. In this mode, the AES-GCM nonce for a packet sent to a
known peer consists of a 32-bit prefix (a per-key salt XOR the peer's
address) followed by a 64-bit counter. That counter is stored in the
peer's RX crypto object. When the peer reports a change in which key
it uses to receive packets, TIPC resets this counter. The sender can
still be using the same TX key and salt, so subsequent packets reuse
earlier nonces. This nonce reuse breaks confidentiality and exposes
GCM's authentication key. This makes forgeries trivial: an attacker
can exploit CTR malleability to alter captured ciphertexts and use the
recovered authentication key to compute a valid tag for the modified
ciphertext, under the same key and nonce.

Use the TX key's existing aead->seqno counter instead. All encryptions
using that key object share the same atomic counter, so concurrent
encryptions get distinct nonce counter values. The counter survives
key activation and peer reconnection, and peer key-status reports
cannot reset it. This prevents those transitions from causing nonce
reuse while the same TX key remains installed.

The nonce format is unchanged, and receivers do not require consecutive
counter values, so sharing the counter across peers remains compatible
with existing receivers. A pre-existing check still invokes key
revocation in the unlikely event that the counter wraps to zero.

## Which versions are affected by CVE-2026-98805?


## How do I fix CVE-2026-98805?

Apply the vendor's patch.

## Is CVE-2026-98805 being exploited?

There is no known exploitation of CVE-2026-98805 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98805 and fix it if it is affected.

What it is: CVE-2026-98805 is a vulnerability in Linux, published on 18 Oct 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-2026-98805 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-2026-98805/ (Markdown: https://insights.sbomify.com/CVE-2026-98805/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98805
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98805
- OSV: https://osv.dev/vulnerability/CVE-2026-98805

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98805/
Summaries are generated and may contain mistakes; the official description above is the record.