# CVE-2026-66034: libssh2 Heap Out-of-Bounds Read via publickey subsystem CVE-2026-66034 is fixed in 11 products on 1 platform, first by libssh2-1t64 1.11.0-4.1ubuntu0.24.04.3, released July 14, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-66034 - Priority: High - CVSS: 7.5 (Important) - EPSS: 0.0040 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Jul 24, 2026 - Weakness: Out-of-bounds Read - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66034 ## Description 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | cargo-c amzn 2023 | 0.10.21-1.amzn2023.0.1 | [ALAS2023-2026-2064](https://patchblox.com/security/data/fix/linux/alas2023-2026-2064.md) | Aug 17, 2026 | | Linux | cargo-c-debuginfo amzn 2023 | 0.10.21-1.amzn2023.0.1 | [ALAS2023-2026-2064](https://patchblox.com/security/data/fix/linux/alas2023-2026-2064.md) | Aug 17, 2026 | | Linux | libssh2 Debian 12.15 (bookworm) | 1.10.0-3+deb12u1 | [DEBIAN-CVE-2026-66034](https://patchblox.com/security/data/fix/linux/debian-cve-2026-66034.md) | Aug 1, 2026 | | Linux | libssh2 Debian 13.5 (trixie) | 1.11.1-1+deb13u2 | [DEBIAN-CVE-2026-66034](https://patchblox.com/security/data/fix/linux/debian-cve-2026-66034.md) | Aug 1, 2026 | | Linux | libssh2 Debian 14 | 1.11.1-5 | [DEBIAN-CVE-2026-66034](https://patchblox.com/security/data/fix/linux/debian-cve-2026-66034.md) | Aug 1, 2026 | | Linux | libssh2 amzn 2023 | 1.10.0-1.amzn2023.0.6 | [ALAS2023-2026-2056](https://patchblox.com/security/data/fix/linux/alas2023-2026-2056.md) | Aug 17, 2026 | | Linux | libssh2-1 Ubuntu 18.04.6 LTS (bionic) | 1.8.0-1ubuntu0.1+esm1 | [libssh2-1 1.8.0-1ubuntu0.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libssh2-1-1.8.0-1ubuntu0.1-esm1.md) | Jul 24, 2026 | | Linux | libssh2-1 Ubuntu 20.04 LTS (focal) | 1.8.0-2.1ubuntu0.1+esm1 | [libssh2-1 1.8.0-2.1ubuntu0.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libssh2-1-1.8.0-2.1ubuntu0.1-esm1.md) | Jul 24, 2026 | | Linux | libssh2-1 Ubuntu 22.04.1 LTS (jammy) | 1.10.0-3ubuntu0.1 | [libssh2-1 1.10.0-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libssh2-1-1.10.0-3ubuntu0.1.md) | Jul 24, 2026 | | Linux | libssh2-1t64 Ubuntu 24.04.5 LTS (noble) | 1.11.0-4.1ubuntu0.24.04.3 | [libssh2-1t64 1.11.0-4.1ubuntu0.24.04.3](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libssh2-1t64-1.11.0-4.1ubuntu0.24.04.3.md) | Jul 14, 2026 | | Linux | libssh2-1t64 Ubuntu 26.04.1 LTS (resolute) | 1.11.1-1ubuntu0.26.04.3 | [libssh2-1t64 1.11.1-1ubuntu0.26.04.3](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libssh2-1t64-1.11.1-1ubuntu0.26.04.3.md) | Jul 24, 2026 | | Linux | libssh2-debuginfo amzn 2023 | 1.10.0-1.amzn2023.0.6 | [ALAS2023-2026-2056](https://patchblox.com/security/data/fix/linux/alas2023-2026-2056.md) | Aug 17, 2026 | | Linux | libssh2-debugsource amzn 2023 | 1.10.0-1.amzn2023.0.6 | [ALAS2023-2026-2056](https://patchblox.com/security/data/fix/linux/alas2023-2026-2056.md) | Aug 17, 2026 | | Linux | libssh2-devel amzn 2023 | 1.10.0-1.amzn2023.0.6 | [ALAS2023-2026-2056](https://patchblox.com/security/data/fix/linux/alas2023-2026-2056.md) | Aug 17, 2026 | | Linux | libssh2-docs amzn 2023 | 1.10.0-1.amzn2023.0.6 | [ALAS2023-2026-2056](https://patchblox.com/security/data/fix/linux/alas2023-2026-2056.md) | Aug 17, 2026 | | Linux | libssh2_org opensuse-leap 16.0 | 1.11.1-160000.5.1 | [OPENSUSE-SU-2026:21549-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21549-1.md) | Aug 10, 2026 | | Linux | libssh2_org sles 15.6 | 1.11.0-150600.20.6.1 | [SUSE-SU-2026:3541-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3541-1.md) | Aug 10, 2026 | | Linux | libssh2_org sles 15.7 | 1.11.0-150600.20.6.1 | [SUSE-SU-2026:3541-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3541-1.md) | Aug 10, 2026 | | Linux | libssh2_org sles 16.0 | 1.11.1-160000.5.1 | [SUSE-SU-2026:23225-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23225-1.md) | Aug 10, 2026 | | Linux | rust-cargo-c-debugsource amzn 2023 | 0.10.21-1.amzn2023.0.1 | [ALAS2023-2026-2064](https://patchblox.com/security/data/fix/linux/alas2023-2026-2064.md) | Aug 17, 2026 | --- Data as of 2026-11-08T06:59:42Z UTC. 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