What is CVE-2019-20396?

CVE-2019-20396 is a medium-severity vulnerability in Cesnet Libyang, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 6.5/10. Published 2020-01-22.

How severe is CVE-2019-20396?

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

Buffer overflow in Cesnet Libyang

CVE-2019-20396

A segmentation fault is present in yyparse in libyang before v1.0-r1 due to a malformed pattern statement value during lys_parse_path parsing.

Vulnerability class: Buffer Overflow

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: 0.019 (79.2th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 79th percentile — 79.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.019 · newest: 0.019 · change: +0.000

Affected products

Cesnet Libyang — versions 0.11, 0.12, 0.13

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

github.com/CESNET/libyang/compare/v0.16-r3...v1.0-r1 (Third Party Advisory)
github.com/CESNET/libyang/issues/740 (Exploit, Third Party Advisory)
github.com/CESNET/libyang/commit/a1f17693904ed6fecc8902c747fc50a8f20e6af8 (Patch, Third Party Advisory)
lists.debian.org/debian-lts-announce/2023/09/msg00019.html (mailing-list)

Frequently asked questions

What is CVE-2019-20396?: CVE-2019-20396 is a medium-severity vulnerability in Cesnet Libyang, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 6.5/10. Published 2020-01-22.
How severe is CVE-2019-20396?: Medium severity. CVSS v3 base score is 6.5 out of 10.