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Vulnerability record · CVE-2026-73564 · published 13 August 2026

CVE-2026-73564: Integer overflow vulnerability

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.

8.7 CVSS 4.0 High EPSS 0.52% · top 57.9% CWE-129 · CWE-129CWE-190 · Integer overflow Deferred
8.7CVSS 4.0 base score
0.52%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
18 Sep 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-73564), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.