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{"affected_release": [{"advisory": "RHSA-2026:46927", "cpe": "cpe:/a:redhat:hummingbird:1", "impact": "important", "package": "libssh2-main-1.11.1-10.2.hum1", "product_name": "Red Hat Hardened Images", "release_date": "2026-07-27T00:00:00Z"}], "bugzilla": {"description": "libssh2: libssh2: Denial of Service via integer underflow in AES-GCM cipher negotiation", "id": "2506853", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2506853"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H", "status": "verified"}, "cwe": "CWE-125", "details": ["A flaw was found in libssh2. A pre-authentication integer underflow vulnerability exists in the `ssh2_cipher_crypt()` function when negotiating AES-GCM ciphers during the handshake. A malicious SSH server can exploit this to trigger an out-of-bounds read and a memory copy operation with an extremely large length argument, leading to an immediate client process crash. This vulnerability results in a Denial of Service (DoS) for any connecting client."], "mitigation": {"lang": "en:us", "value": "To mitigate the vulnerability, developers or administrators must configure the specific applications utilizing libssh2 to explicitly exclude AES-GCM from their preferred cipher lists."}, "name": "CVE-2026-66033", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "libssh2", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "libssh2", "product_name": "Red Hat Enterprise Linux 7"}], "public_date": "2026-07-24T16:35:28Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-66033\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-66033\nhttps://github.com/libssh2/libssh2/commit/a2ed82d40964bbc0d64cd717aa0a5a892117d2e6\nhttps://github.com/libssh2/libssh2/pull/2401\nhttps://www.vulncheck.com/advisories/libssh2-integer-underflow-dos-via-aes-gcm-cipher-negotiation"], "statement": "This Moderate impact flaw in libssh2 allows a malicious SSH server to trigger a client-side denial of service. The vulnerability, an integer underflow during AES-GCM cipher negotiation, can cause a connecting client to crash before authentication. Exploitation requires the client to connect to a specially crafted, untrusted SSH server.", "threat_severity": "Moderate"}