frp: Unauthenticated Remote Denial of Service in the frp SSH Tunnel Gateway via Integer Overflow
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-129 and the CVSS impact.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| fatedier | frp | 0.53.0 to before 0.70.1 | 0.70.1 | Patch available | CNA |
| — | github.com/fatedier/frp (Go) | 0.53.0 to before 0.70.1 | 0.70.1 | Patch available | GHSA-26gq-p25f-99cp |
- frp Vendorfatedier Affected 0.53.0 to before 0.70.1 Fixed in 0.70.1 Patch available CNA
- github.com/fatedier/frp (Go) Vendor— Affected 0.53.0 to before 0.70.1 Fixed in 0.70.1 Patch available GHSA-26gq-p25f-99cp
Remediation
- Fix · CNA frp (fatedier) Fixed in 0.70.1
- Fix · GHSA-26gq-p25f-99cp github.com/fatedier/frp (Go) Fixed in 0.70.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-73564
- 2026-10-03 Alias added: GHSA-26gq-p25f-99cp
References
More fatedier vulnerabilities
- TI-2026-29566 frp: Authentication bypass in frp HTTP vhost routing when routeByHTTPUser is used for access control CVSS 3.1CRITICAL 9.1
- TI-2026-74113 Missing authentication exposes pprof debug endpoints in frp CVSS 4.0MEDIUM 6.3
Sources
- CVE-2026-73564 · CVE Program
- CVE-2026-73564 · NVD
- FIRST EPSS
- GHSA-26gq-p25f-99cp · GitHub Advisory Database · CC BY 4.0
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