Heap disclosure and corruption via unchecked comment length
Published Jul 24, 2026 · Updated Jul 24, 2026
Out-of-bounds reads in libssh2 1.11.1 and earlier allow remote attackers to disclose heap data via crafted SSH publickey responses. The libssh2_publickey_list_fetch() version 1 parser advances by a server-controlled comment_len without checking the remaining buffer, then frees an uninitialized pointer on error. Reachability requires a consuming application to request a publickey list from an attacker-controlled SSH server; resulting reads expose adjacent heap data and cleanup corrupts allocator state.
Summary
What happened
Out-of-bounds reads in libssh2 1.11.1 and earlier allow remote attackers to disclose heap data via crafted SSH publickey responses. The libssh2_publickey_list_fetch() version 1 parser advances by a server-controlled comment_len without checking the remaining buffer, then frees an uninitialized pointer on error. Reachability requires a consuming application to request a publickey list from an attacker-controlled SSH server; resulting reads expose adjacent heap data and cleanup corrupts allocator state.
The record
- CVE
- CVE-2026-66034
- Published
- Jul 24, 2026
- Updated
- Jul 24, 2026
- Vendor
- libssh2
- Product
- libssh2
- Classifications
- CWE-908, CWE-125
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 24, 2026CVE publishedPublication date reported by the CVE source.
- Jul 24, 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=1.11.1
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.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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