Vulnerability Details CVE-2026-66034
libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.003
EPSS Ranking 17.0%
CVSS Severity
CVSS v3 Score 7.5
Products affected by CVE-2026-66034
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cpe:2.3:a:libssh2:libssh2:-
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cpe:2.3:a:libssh2:libssh2:0.1
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cpe:2.3:a:libssh2:libssh2:0.10
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cpe:2.3:a:libssh2:libssh2:0.11
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cpe:2.3:a:libssh2:libssh2:0.12
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cpe:2.3:a:libssh2:libssh2:0.13
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cpe:2.3:a:libssh2:libssh2:0.14
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cpe:2.3:a:libssh2:libssh2:0.15
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cpe:2.3:a:libssh2:libssh2:0.16
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cpe:2.3:a:libssh2:libssh2:0.17
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cpe:2.3:a:libssh2:libssh2:0.18
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cpe:2.3:a:libssh2:libssh2:0.3
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cpe:2.3:a:libssh2:libssh2:0.5
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cpe:2.3:a:libssh2:libssh2:0.6
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cpe:2.3:a:libssh2:libssh2:0.7
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cpe:2.3:a:libssh2:libssh2:0.8
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cpe:2.3:a:libssh2:libssh2:1.0
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cpe:2.3:a:libssh2:libssh2:1.1
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cpe:2.3:a:libssh2:libssh2:1.10.0
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cpe:2.3:a:libssh2:libssh2:1.2
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cpe:2.3:a:libssh2:libssh2:1.2.1
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cpe:2.3:a:libssh2:libssh2:1.2.2
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cpe:2.3:a:libssh2:libssh2:1.2.3
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cpe:2.3:a:libssh2:libssh2:1.2.4
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cpe:2.3:a:libssh2:libssh2:1.2.5
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cpe:2.3:a:libssh2:libssh2:1.2.6
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cpe:2.3:a:libssh2:libssh2:1.2.7
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cpe:2.3:a:libssh2:libssh2:1.2.8
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cpe:2.3:a:libssh2:libssh2:1.2.9
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cpe:2.3:a:libssh2:libssh2:1.3.0
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cpe:2.3:a:libssh2:libssh2:1.4.0
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cpe:2.3:a:libssh2:libssh2:1.4.1
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cpe:2.3:a:libssh2:libssh2:1.4.2
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cpe:2.3:a:libssh2:libssh2:1.4.3
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cpe:2.3:a:libssh2:libssh2:1.5.0
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cpe:2.3:a:libssh2:libssh2:1.6.0
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cpe:2.3:a:libssh2:libssh2:1.7.0
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cpe:2.3:a:libssh2:libssh2:1.8.0
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cpe:2.3:a:libssh2:libssh2:1.8.1
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cpe:2.3:a:libssh2:libssh2:1.8.2
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cpe:2.3:a:libssh2:libssh2:1.9.0