Vulnerability · Published Oct 7, 2026 · Assigned by wolfSSL

CVE-2026-83540wolfSSHd on Windows race condition leading to logon token reused across connections

High 7.7

In plain English

A high-severity improper authentication in wolfSSH from wolfSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 46% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)7.7High

Exploit odds (30 days)0.6%top 53.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

When password or public key authentication is used with the Windows port of wolfSSHd, the Windows logon token acquired for one authenticated connection is not released before a token is acquired for a subsequent connection, resulting in user login poisoning between connections. A less privileged user with a valid account on the server can exploit this to force a login as a more privileged user. The vulnerability was introduced with the initial Windows port of wolfSSHd in wolfSSH version 1.4.15 and affects all versions through 1.5.0. Non-Windows builds of wolfSSHd are not affected.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Alpine:v3.24	wolfssh	1.6.0-r0	ALPINE-CVE-2026-83540

Affected products (as reported)

Vendor	Product	Versions
wolfSSL	wolfSSH	1.4.15 – through 1.5.0

Weakness: CWE-287, CWE-613 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References

wolfSSH source repository product
Fix: give each Windows wolfSSHd connection its own authentication context patch
Fix: add Windows sanity close of token before acquiring a new one patch
wolfSSL security vulnerabilities page vendor-advisory