# CVE-2026-24904: TrustTunnel has `client_random_prefix` rule bypass via fragmented or partial TLS ClientHello

> Attackers can bypass client_random_prefix filtering rules in TrustTunnel by sending fragmented TLS ClientHello messages, allowing unauthorized traffic to pass through.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Jan 2026
- **Updated:** 29 Jan 2026
- **Also known as:** GHSA-fqh7-r5gf-3r87

## What is CVE-2026-24904?

CVE-2026-24904 is a medium-severity vulnerability in TrustTunnel, published on 29 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

TrustTunnel is an open-source VPN protocol with a rule bypass issue in versions prior to 0.9.115. In `tls_listener.rs`, `TlsListener::listen()` peeks 1024 bytes and calls `extract_client_random(...)`. If `parse_tls_plaintext` fails (for example, a fragmented/partial ClientHello split across TCP writes), `extract_client_random` returns `None`. In `rules.rs`, `RulesEngine::evaluate` only evaluates `client_random_prefix` when `client_random` is `Some(...)`. As a result, when extraction fails (`client_random == None`), any rule that relies on `client_random_prefix` matching is skipped and evaluation falls through to later rules. As an important semantics note: `client_random_prefix` is a match condition only. It does not mean "block non-matching prefixes" by itself. A rule with `client_random_prefix = ...` triggers its `action` only when the prefix matches (and the field is available to evaluate). Non-matches (or `None`) simply do not match that rule and continue to fall through. The vulnerability is fixed in version 0.9.115.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-24904?

It affects 1 product.


Products: Adguard Trusttunnel.

## How do I fix CVE-2026-24904?

No fix has been published for CVE-2026-24904 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-24904 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-24904 exists.

## Other vulnerabilities in TrustTunnel

- [CVE-2026-24902](https://insights.sbomify.com/CVE-2026-24902/): TrustTunnel has SSRF and private network restriction bypass via numeric address destinations (high 7.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-24904 and fix it if it is affected.

What it is: CVE-2026-24904 is a medium-severity vulnerability in TrustTunnel, published on 29 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-24904 exists.

Affected product: TrustTunnel. 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-2026-24904/ (Markdown: https://insights.sbomify.com/CVE-2026-24904/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-24904
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-24904
- OSV: https://osv.dev/vulnerability/CVE-2026-24904

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-24904/
Summaries are generated and may contain mistakes; the official description above is the record.