CVE-2026-39830
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk48th percentile - higher than 48% of all known CVEs
Summary
In an SSH library (likely Go), a malicious SSH peer can send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine cannot be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded.
Risk Assessment
An attacker could exhaust server resources by blocking connections and leaking goroutines, potentially leading to denial of service (DoS).
Recommendation
Update the SSH library to a version that discards unsolicited global responses.
Other vulnerabilities in SSH library
See all- CVE-2026-39834Critical
When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused an infinite loop sending empty packets. The fix uses int64 for size comparison to prevent truncation.
- CVE-2026-56855High
After a channel is established, a malicious peer could send crafted messages causing a deadlock of the entire connection. Now all RFC 4254 channel messages are handled, and global requests are explicitly processed. Other messages are treated as protocol errors and the connection is torn down instead of buffering and blocking.
Original NVD description (English source)
A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine could not be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS