CVE-2026-55200

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{"bugzilla": {"description": "libssh2: libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c", "id": "2490127", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2490127"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.1", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["libssh2 through 1.11.1, fixed in commit 7acf3df contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.", "An out-of-bounds write vulnerability exists in the libssh2 client. A remote attacker can exploit this by sending a specially crafted SSH packet with an abnormally large length value. This corrupts the application's memory and can potentially allow the attacker to execute arbitrary code on the affected system."], "mitigation": {"lang": "en:us", "value": "The primary mitigation is strict network access control. Ensure libssh2 clients only connect to trusted SSH servers, and use firewalls to block untrusted incoming connections if libssh2 is deployed as a server-side application."}, "name": "CVE-2026-55200", "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"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Affected", "package_name": "libssh2", "product_name": "Red Hat Hardened Images"}], "public_date": "2026-06-17T19:03:15Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-55200\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-55200\nhttps://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8\nhttps://github.com/libssh2/libssh2/pull/2052\nhttps://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c"], "statement": "An Important-rated out-of-bounds write vulnerability in libssh2 allows unauthenticated remote attackers to execute arbitrary code. By sending oversized, maliciously crafted SSH packets, an attacker can corrupt system memory and compromise the host.\nNote: Red Hat Enterprise Linux (RHEL) 8 and newer are not affected by this flaw, as they do not ship the libssh2 package..", "threat_severity": "Important"}

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