CVE-2026-59848 Libssh: libssh: denial of service via sftp responses with unknown request ids
A malicious SFTP server can cause client-side denial of service in libssh by sending responses with unknown request IDs, leading to unbounded memory growth.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59848?
CVE-2026-59848 is a medium-severity denial of service vulnerability in Redhat Enterprise Linux, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A flaw was found in libssh. A malicious SFTP server can send responses for unknown request IDs that libssh clients keep queued indefinitely, causing unbounded memory growth and client-side denial of service.
Weakness: CWE-770
Which versions are affected by CVE-2026-59848?
It affects 3 products.
Products include Libssh Libssh, Redhat Enterprise Linux, Redhat Hardened Images.
How do I fix CVE-2026-59848?
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-2026-59848 being exploited?
There is no known exploitation of CVE-2026-59848 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-93240, BELL-CVE-2026-59848, DEBIAN-CVE-2026-59848, ECHO-b7fc-a7ac-f445, GHSA-4h4r-q9xg-gfmm, UBUNTU-CVE-2026-59848.