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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
Which versions are affected by CVE-2026-24904?
It affects 1 product.
Products include 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
Sources
Also known as GHSA-fqh7-r5gf-3r87.