What is CVE-2019-20398?

CVE-2019-20398 is a medium-severity vulnerability in Cesnet Libyang, classified under NULL Pointer Dereference. CVSS score: 6.5/10. Published 2020-01-22.

How severe is CVE-2019-20398?

Medium severity. CVSS v3 base score is 6.5 out of 10.

NULL pointer dereference in Cesnet Libyang

CVE-2019-20398

A NULL pointer dereference is present 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.

Published 2020-01-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.018 (77.9th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 78th percentile — 77.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.018 · newest: 0.018 · change: 0.000

Affected products

Cesnet Libyang — versions 0.11, 0.12, 0.13

Weakness classification (CWE)

CWE-476 — NULL Pointer Dereference

References

github.com/CESNET/libyang/compare/v1.0-r2...v1.0-r3 (Third Party Advisory)
github.com/CESNET/libyang/commit/7852b272ef77f8098c35deea6c6f09cb78176f08 (Patch)
github.com/CESNET/libyang/issues/773 (Exploit, Third Party Advisory)
bugzilla.redhat.com/show_bug.cgi (Patch, Third Party Advisory, Issue Tracking)
lists.debian.org/debian-lts-announce/2023/09/msg00019.html (mailing-list)

Frequently asked questions

What is CVE-2019-20398?: CVE-2019-20398 is a medium-severity vulnerability in Cesnet Libyang, classified under NULL Pointer Dereference. CVSS score: 6.5/10. Published 2020-01-22.
How severe is CVE-2019-20398?: Medium severity. CVSS v3 base score is 6.5 out of 10.