#VU19258 Integer overflow in libssh2 - CVE-2019-13115

Vulnerability identifier: #VU19258

Vulnerability risk: Medium

CVSSv4.0: 6.2 [CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2019-13115

CWE-ID: CWE-190

Exploitation vector: Network

Exploit availability: Yes

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

Vendor: libssh2.org

Description

The vulnerability allows a remote attacker to execute arbitrary code or cause a denial of service (DoS) condition on a targeted system.

The vulnerability exists due to integer overflow in the "kex_method_diffie_hellman_group_exchange_sha256_key_exchange" function in the "kex.c" file. A remote attacker can trick a victim to connect to an attacker-controlled Secure Shell (SSH) server, which would allow the attacker to send packets that submit malicious input to the targeted system, trigger integer overflow leading to an out-of-bounds write condition and execute arbitrary code or cause a DoS condition.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

libssh2: 0.1 - 1.8.2

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External links
https://blog.semmle.com/libssh2-integer-overflow/
https://github.com/libssh2/libssh2/compare/02ecf17...42d37aa
https://github.com/libssh2/libssh2/pull/350
https://libssh2.org/changes.html

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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.