CVE-2026-59845 Libssh: libssh: denial of service via unchecked proxycommand fork() failure
An attacker can cause local denial of service in libssh by triggering a fork failure during ProxyCommand execution, leading to invalid process ID handling.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-59845?
CVE-2026-59845 is a medium-severity denial of service vulnerability in Redhat Enterprise Linux, published on 21 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
A flaw was found in libssh. When ProxyCommand is used, an unchecked fork() failure can be stored as process ID -1; during cleanup, signals may then be sent across the caller's accessible process tree, leading to local denial of service.
Weakness: CWE-390
Which versions are affected by CVE-2026-59845?
It affects 3 products.
Products include Libssh Libssh, Redhat Enterprise Linux, Redhat Hardened Images.
How do I fix CVE-2026-59845?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-59845 being exploited?
There is no known exploitation of CVE-2026-59845 in the wild and no public exploit code.
Other vulnerabilities in Redhat Enterprise Linux
- CVE-2026-59851 Libssh: libssh: authentication bypass via missing gssapi principal check
- CVE-2025-5987 Libssh: invalid return code for chacha20 poly1305 with openssl backend
- CVE-2025-14821 Libssh: libssh: insecure default configuration leads to local man-in-the-middle attacks on windows
- CVE-2012-4560 Memory corruption in n/a
- CVE-2012-4562 Integer overflow in n/a
Sources
Also known as AZL-93249, BELL-CVE-2026-59845, DEBIAN-CVE-2026-59845, ECHO-d722-762e-9126, GHSA-97fp-2vw9-q5jg, UBUNTU-CVE-2026-59845.