CVE-2026-39834 is a critical-severity integer overflow or wraparound vulnerability in golang.org/x/crypto/ssh (go), affecting versions < 0.52.0. It is fixed in 0.52.0.
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.
An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value. Typical impact: incorrect size calculations leading to heap overflows or logic errors.
CVE-2026-39834 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (0.52.0). Upgrading removes the vulnerable code path.
go
golang.org/x/crypto/ssh (< 0.52.0)golang.org/x/crypto/ssh → 0.52.0 (go)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-39834 is reachable in your applications. Explore open-source security for your team.
See if CVE-2026-39834 is reachable in your applications. Get a demo
Already deployed Kodem? See CVE-2026-39834 in your environment →Upgrade golang.org/x/crypto/ssh to 0.52.0 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-39834 is a critical-severity integer overflow or wraparound vulnerability in golang.org/x/crypto/ssh (go), affecting versions < 0.52.0. It is fixed in 0.52.0. An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value.
CVE-2026-39834 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
golang.org/x/crypto/ssh (go) versions < 0.52.0 is affected.
Yes. CVE-2026-39834 is fixed in 0.52.0. Upgrade to this version or later.
Whether CVE-2026-39834 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade golang.org/x/crypto/ssh to 0.52.0 or later.