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CVE-2026-66034

CVE-2026-66034 · libssh2 Heap Out-of-Bounds Read via publickey subsystem

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 7.7 · High · EPSS 0.4% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • libssh2

    Versions
    • ≥ 0, ≤ 1.11.1: Affected (semver)
    • a13bb6c773f0d55ad1628cede57e99803cd898d9: Not affected (git)

    No fix published

  • libssh2 Debian:12

    Versions
    • 1.10.0-3
    Affected ranges
    • ECOSYSTEM: < 1.10.0-3+deb12u1

    Update to 1.10.0-3+deb12u1

  • libssh2 Debian:13

    Versions
    • 1.11.1-1
    • 1.11.1-1+deb13u1
    Affected ranges
    • ECOSYSTEM: < 1.11.1-1+deb13u2

    Update to 1.11.1-1+deb13u2

  • libssh2 Debian:14

    Versions
    • 1.11.1-1
    • 1.11.1-2
    • 1.11.1-3
    • 1.11.1-4
    Affected ranges
    • ECOSYSTEM: < 1.11.1-5

    Update to 1.11.1-5

  • libssh2 Ubuntu:Pro:14.04:LTS

    Versions
    • 1.4.3-1
    • 1.4.3-2
    • 1.4.3-2ubuntu0.1
    • 1.4.3-2ubuntu0.2
    • 1.4.3-2ubuntu0.2+esm1
    • 1.4.3-2ubuntu0.2+esm2
    • 1.4.3-2ubuntu0.2+esm3
    Affected ranges
    • ECOSYSTEM: < 1.4.3-2ubuntu0.2+esm4

    Update to 1.4.3-2ubuntu0.2+esm4

  • libssh2 Ubuntu:Pro:16.04:LTS

    Versions
    • 1.5.0-2
    • 1.5.0-2ubuntu0.1
    • 1.5.0-2ubuntu0.1+esm1
    • 1.5.0-2ubuntu0.1+esm2
    Affected ranges
    • ECOSYSTEM: < 1.5.0-2ubuntu0.1+esm3

    Update to 1.5.0-2ubuntu0.1+esm3

  • libssh2 Ubuntu:Pro:18.04:LTS

    Versions
    • 1.8.0-1
    • 1.8.0-1ubuntu0.1
    Affected ranges
    • ECOSYSTEM: < 1.8.0-1ubuntu0.1+esm1

    Update to 1.8.0-1ubuntu0.1+esm1

  • libssh2 Ubuntu:Pro:20.04:LTS

    Versions
    • 1.8.0-2.1build1
    • 1.8.0-2.1ubuntu0.1
    Affected ranges
    • ECOSYSTEM: < 1.8.0-2.1ubuntu0.1+esm1

    Update to 1.8.0-2.1ubuntu0.1+esm1

  • libssh2 Ubuntu:22.04:LTS

    Versions
    • 1.9.0-3
    • 1.10.0-2
    • 1.10.0-2build1
    • 1.10.0-3
    Affected ranges
    • ECOSYSTEM: < 1.10.0-3ubuntu0.1

    Update to 1.10.0-3ubuntu0.1

  • libssh2 Ubuntu:24.04:LTS

    Versions
    • 1.11.0-2
    • 1.11.0-3
    • 1.11.0-4
    • 1.11.0-4.1build1
    • 1.11.0-4.1build2
    • 1.11.0-4.1ubuntu0.24.04.1
    • 1.11.0-4.1ubuntu0.24.04.2
    Affected ranges
    • ECOSYSTEM: < 1.11.0-4.1ubuntu0.24.04.3

    Update to 1.11.0-4.1ubuntu0.24.04.3

  • libssh2 Ubuntu:26.04:LTS

    Versions
    • 1.11.1-1build1
    • 1.11.1-1build2
    • 1.11.1-1ubuntu0.26.04.1
    • 1.11.1-1ubuntu0.26.04.2
    Affected ranges
    • ECOSYSTEM: < 1.11.1-1ubuntu0.26.04.3

    Update to 1.11.1-1ubuntu0.26.04.3

Original sources

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