#VU34868 NULL pointer dereference in libyang - CVE-2019-20398

Vulnerability identifier: #VU34868

Vulnerability risk: Medium

CVSSv4.0: 4.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2019-20398

CWE-ID: CWE-476

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
libyang
Universal components / Libraries / Libraries used by multiple products

Vendor: CESNET

Description

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

The vulnerability exists due to a NULL pointer dereference error in libyang before v1.0-r3 in the function lys_extension_instances_free() due to a copy of unresolved extensions in lys_restr_dup(). Applications that use libyang to parse untrusted input yang files may crash. A remote attacker can perform a denial of service (DoS) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

libyang: 0.11 - 1.0

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External links
http://bugzilla.redhat.com/show_bug.cgi?id=1793935
http://github.com/CESNET/libyang/commit/7852b272ef77f8098c35deea6c6f09cb78176f08
http://github.com/CESNET/libyang/compare/v1.0-r2...v1.0-r3
http://github.com/CESNET/libyang/issues/773

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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.