CVE-2025-4877

CVE-2025-4877 is a medium-severity vulnerability with a CVSS 3.x base score of 4.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

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.

Frequently asked questions

What is CVE-2025-4877?
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.
How severe is CVE-2025-4877?
CVE-2025-4877 has a CVSS 3.x base score of 4.5, rated medium severity. It is exploitable over local access with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2025-4877 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-4877?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-4877 have an EU (EUVD) identifier?
Yes. CVE-2025-4877 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-28257.
When was CVE-2025-4877 published?
CVE-2025-4877 was published on 2025-08-20 and last updated on 2026-06-30.

References

Other CWE-787 (Out-of-bounds Write) vulnerabilities

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