Vulnerability · Published May 22, 2026 · Assigned by Go
CVE-2026-39834Invoking infinite loop on large channel writes in golang.org/x/crypto/ssh
Critical 9.1
In plain English
A critical-severity security flaw in golang.org/x/crypto/ssh from golang.org/x/crypto. 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 49% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.6%top 51.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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 the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | golang-go.crypto | no fix listed | DEBIAN-CVE-2026-39834 |
| Debian:13 | golang-go.crypto | no fix listed | DEBIAN-CVE-2026-39834 |
| Debian:14 | golang-go.crypto | 1:0.52.0-1 | DEBIAN-CVE-2026-39834 |
| Go | golang.org/x/crypto | 0.52.0 | GO-2026-5020 |
| Go | golang.org/x/crypto | 0.52.0 | GHSA-rm3j-f69w-wqmq |
| Ubuntu:25.10 | golang-go.crypto | no fix listed | UBUNTU-CVE-2026-39834 |
| Ubuntu:22.04:LTS | google-guest-agent | 20250116.00-0ubuntu1~22.04.3 | UBUNTU-CVE-2026-39834 |
| Ubuntu:24.04:LTS | google-guest-agent | 20250116.00-0ubuntu1~24.04.4 | UBUNTU-CVE-2026-39834 |
| Ubuntu:25.10 | google-guest-agent | 20250506.01-0ubuntu1.2 | UBUNTU-CVE-2026-39834 |
| Ubuntu:26.04:LTS | google-guest-agent | 20250506.01-0ubuntu2.1 | UBUNTU-CVE-2026-39834 |
| Ubuntu:22.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-39834 |
| Ubuntu:24.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-39834 |
| Ubuntu:25.10 | snapd | no fix listed | UBUNTU-CVE-2026-39834 |
| Ubuntu:26.04:LTS | snapd | no fix listed | UBUNTU-CVE-2026-39834 |
| Ubuntu:26.10 | snapd | no fix listed | UBUNTU-CVE-2026-39834 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| golang.org/x/crypto | golang.org/x/crypto/ssh | 0 – before 0.52.0 |