Vulnerability identifier: #VU22574

Vulnerability risk: High

CVSSv3.1: 7.3 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-17498

CWE-ID: CWE-190

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
libssh2
Client/Desktop applications / Software for system administration

Vendor: libssh2.org

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack or access sensitive information.

The vulnerability exists due to integer overflow in the "SSH_MSG_DISCONNECT" logic in "packet.c" in a bounds check. A remote attacker can specify an arbitrary (out-of-bounds) offset for a subsequent memory read, trigger out-of-bounds read, disclose sensitive information or cause a denial of service condition on the target system when a user connects to the malicious SSH server.

Mitigation
Install update from vendor's website.

Vulnerable software versions

libssh2: 0.1 - 1.9.0

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External links
http://blog.semmle.com/libssh2-integer-overflow-CVE-2019-17498/
http://github.com/kevinbackhouse/SecurityExploits/tree/8cbdbbe6363510f7d9ceec685373da12e6fc752d/libssh2/out_of_bounds_read_disconnect_CVE-2019-17498
http://github.com/libssh2/libssh2/blob/42d37aa63129a1b2644bf6495198923534322d64/src/packet.c#L480
http://github.com/libssh2/libssh2/pull/402/commits/1c6fa92b77e34d089493fe6d3e2c6c8775858b94
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TY7EEE34RFKCTXTMBQQWWSLXZWSCXNDB/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.