# 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.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Aug 2026
- **Updated:** 13 Aug 2026
- **Also known as:** GHSA-26gq-p25f-99cp, GO-2026-6103

## 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.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2026-73564?

3 open source packages ship an affected version, including github.com/fatedier/frp.


| Package | Ecosystem | 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73564 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73564 exists.

Affected packages and fixed versions:
- github.com/fatedier/frp (Go): affected from 0.53.0; fixed in 0.70.1
- github.com/fatedier/frp (Go): affected from 0.53.0; fixed in 0.70.1
- github.com/fatedier/frp (Go): affected from 0.53.0; fixed in 0.70.1

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-2026-73564/ (Markdown: https://insights.sbomify.com/CVE-2026-73564/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73564
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73564
- OSV: https://osv.dev/vulnerability/CVE-2026-73564

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73564/
Summaries are generated and may contain mistakes; the official description above is the record.