# CVE-2026-32953: Tillitis: TKey Client has an Error in Protocol Implementation

> A bug in the TKey client library causes certain user-supplied secrets to be ignored, resulting in predictable key material and weakened security.

- **Severity:** Medium 4.7 (`CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:H/SI:H/SA:H`)
- **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:** 20 Mar 2026
- **Updated:** 20 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-32953, GHSA-4w7r-3222-8h6v, GO-2026-4728, UBUNTU-CVE-2026-32953

## What is CVE-2026-32953?

CVE-2026-32953 is a medium-severity vulnerability in tillitis tkeyclient, published on 20 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Tillitis TKey Client package is a Go package for a TKey client. Versions 1.2.0 and below contain a critical bug in the tkeyclient Go module which causes 1 out of every 256 User Supplied Secrets (USS) to be silently ignored, producing the same Compound Device Identifier (CDI)—and thus the same key material—as if no USS is provided. This happens because a buffer index error overwrites the USS-enabled boolean with the first byte of the USS digest, so any USS whose hash starts with 0x00 is effectively discarded. This issue has been fixed in version 1.3.0. Users unable to upgrade immediately should switch to a USS whose hash does not begin with a zero byte.

Weakness: CWE-303 (Incorrect Implementation of Authentication Algorithm)

## Which versions are affected by CVE-2026-32953?

3 open source packages ship an affected version, including github.com/tillitis/tkeyclient. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/tillitis/tkeyclient` | Go | All versions | 1.3.0 |
| `github.com/tillitis/tkeyclient` | Go | All versions | 1.3.0 |
| `github.com/tillitis/tkeyclient` | Go | All versions | 1.3.0 |

Products: Tillitis Tkey Client.

## How do I fix CVE-2026-32953?

Upgrade github.com/tillitis/tkeyclient to 1.3.0 or later.

## Is CVE-2026-32953 being exploited?

There is no known exploitation of CVE-2026-32953 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-32953 and fix it if it is affected.

What it is: CVE-2026-32953 is a medium-severity vulnerability in tillitis tkeyclient, published on 20 Mar 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-2026-32953 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/tillitis/tkeyclient (Go): affected all versions; fixed in 1.3.0
- github.com/tillitis/tkeyclient (Go): affected all versions; fixed in 1.3.0
- github.com/tillitis/tkeyclient (Go): affected all versions; fixed in 1.3.0

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-2026-32953/ (Markdown: https://insights.sbomify.com/CVE-2026-32953/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-32953
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32953
- OSV: https://osv.dev/vulnerability/CVE-2026-32953

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-32953/
Summaries are generated and may contain mistakes; the official description above is the record.