CVE-2025-4877 Libssh: write beyond bounds in binary to base64 conversion functions
An integer overflow in libssh's base64 conversion can cause heap corruption and potential code execution on 32-bit systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-4877?
CVE-2025-4877 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 20 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
There's a vulnerability in the libssh package where when a libssh consumer passes in an unexpectedly large input buffer to ssh_get_fingerprint_hash() function. In such cases the bin_to_base64() function can experience an integer overflow leading to a memory under allocation, when that happens it's possible that the program perform out of bounds write leading to a heap corruption. This issue affects only 32-bits builds of libssh.
Weakness: CWE-787
Which versions are affected by CVE-2025-4877?
How do I fix CVE-2025-4877?
Apply the vendor's patch.
Is CVE-2025-4877 being exploited?
There is no known exploitation of CVE-2025-4877 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-4877, DEBIAN-CVE-2025-4877, GHSA-pwrf-jm93-99r3, UBUNTU-CVE-2025-4877.