CVE-2025-4877 is a medium severity vulnerability affecting the libssh package, specifically in 32-bit builds. The issue arises when the ssh_get_fingerprint_hash() function receives an unexpectedly large input buffer. This input triggers an integer overflow in the bin_to_base64() function, which leads to memory under allocation. Consequently, this can cause an out-of-bounds write operation on the heap, resulting in heap corruption. Heap corruption can destabilize the affected application, potentially leading to crashes or unpredictable behavior. The vulnerability requires local access (attack vector: local) with high attack complexity, low privileges, and no user interaction. The impact on confidentiality, integrity, and availability is limited but present, as indicated by the CVSS vector (C:L/I:L/A:L). No known exploits are currently reported in the wild, and no patches or fixes are referenced in the provided data. This vulnerability is specific to 32-bit builds of libssh, which is a widely used SSH library implemented in various applications and devices for secure communications. The integer overflow and subsequent heap corruption could be leveraged by attackers to cause denial of service or potentially escalate privileges if combined with other vulnerabilities, although exploitation is non-trivial due to the high complexity and local access requirements.

For European organizations, the impact of CVE-2025-4877 depends on the extent to which 32-bit libssh builds are in use within their infrastructure. Many legacy systems, embedded devices, or specialized industrial control systems may still rely on 32-bit architectures and libssh for secure communications. Exploitation could lead to application crashes or instability, potentially disrupting critical services that depend on SSH for secure remote management or data transfer. While the confidentiality and integrity impact is limited, availability could be affected if critical systems become unstable or crash. Organizations in sectors such as manufacturing, energy, telecommunications, and government that use embedded or legacy 32-bit systems are at higher risk. The lack of known exploits reduces immediate threat, but the presence of a memory corruption vulnerability warrants proactive mitigation to prevent future exploitation attempts. Additionally, the medium severity rating suggests that while the threat is not critical, it should not be ignored, especially in environments where stability and security are paramount.

1. Identify and inventory all systems and applications using libssh, focusing on 32-bit builds. 2. Where possible, upgrade to 64-bit builds or newer versions of libssh that are not affected by this vulnerability. 3. If upgrading is not immediately feasible, implement strict input validation and sanitization on any inputs passed to ssh_get_fingerprint_hash() to prevent oversized buffers. 4. Employ runtime protections such as Address Space Layout Randomization (ASLR) and heap protection mechanisms to mitigate the impact of heap corruption. 5. Monitor logs and system behavior for signs of crashes or abnormal activity related to SSH services. 6. Limit local access to systems running vulnerable libssh versions to trusted personnel only, reducing the attack surface. 7. Engage with vendors or open-source maintainers to obtain patches or updates addressing this vulnerability as they become available. 8. Incorporate this vulnerability into vulnerability management and patching cycles to ensure timely remediation.