Heap corruption via undersized Base64 allocation
Published Aug 20, 2025 · Updated Aug 31, 2026
Out-of-bounds write in libssh before 0.11.2 allows local users to corrupt heap memory through an oversized fingerprint-hash input. In src/base64.c, bin_to_base64() overflows its allocation-size calculation and allocates too little memory before encoding the supplied buffer. Reachability requires a 32-bit build and a consumer that passes an attacker-influenced buffer larger than 1 GB to ssh_get_fingerprint_hash().
Summary
What happened
Out-of-bounds write in libssh before 0.11.2 allows local users to corrupt heap memory through an oversized fingerprint-hash input. In src/base64.c, bin_to_base64() overflows its allocation-size calculation and allocates too little memory before encoding the supplied buffer. Reachability requires a 32-bit build and a consumer that passes an attacker-influenced buffer larger than 1 GB to ssh_get_fingerprint_hash().
The record
- CVE
- CVE-2025-4877
- Published
- Aug 20, 2025
- Updated
- Aug 31, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 9
- Classifications
- CWE-787
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 20, 2025CVE publishedPublication date reported by the CVE source.
- Aug 31, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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