CVE-2026-73564 frp: Unauthenticated Remote Denial of Service in the frp SSH Tunnel Gateway via Integer Overflow
An unauthenticated attacker can crash the frp server via an integer overflow in the optional SSH Tunnel Gateway, requiring no authorized-keys file.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73564?
CVE-2026-73564 is a high-severity vulnerability in fatedier frp, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
frp is a fast reverse proxy. From 0.53.0 until 0.70.1, frp's optional SSH Tunnel Gateway in pkg/ssh/server.go parses an SSH exec channel request by adding 4 to an attacker-controlled four-byte big-endian length. A length of 0xFFFFFFFF makes the uint32 addition wrap to 3, defeats the payload bounds check, and causes payload[4:3] to panic in TunnelServer.handleNewChannel. When no authorized-keys file is configured, sshConfig.NoClientAuth permits an unauthenticated peer to reach this channel phase before the frp token is checked, so a single five-byte request terminates the frps process and drops every active tunnel. This issue is fixed in version 0.70.1.
Which versions are affected by CVE-2026-73564?
3 open source packages ship an affected version, including github.com/fatedier/frp.
| Package | Affected | Fixed in |
|---|---|---|
github.com/fatedier/frp Go | From 0.53.0 | 0.70.1 |
github.com/fatedier/frp Go | From 0.53.0 | 0.70.1 |
github.com/fatedier/frp Go | From 0.53.0 | 0.70.1 |
How do I fix CVE-2026-73564?
Upgrade github.com/fatedier/frp to 0.70.1 or later.
Is CVE-2026-73564 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73564 exists.
Sources
Also known as GHSA-26gq-p25f-99cp, GO-2026-6103.