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Fencer Vulns
medium 6.5

CVE-2019-20398 json

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…

published 2020-01-22 6 y ago modified 2026-06-17 4 mo ago also EUVD-2019-10948

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.8%
EPSS 1.8% chance of exploitation in 30 days, percentile 78%
public exploits
0
none known

Summary

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.

Patch / fix

  • libyang Debian 14, Debian 13 1.0.176-1

debian advisories DEBIAN-CVE-2019-20398

  • libyang RHEL 8 1.0.184-1.el8

red hat advisories RHEA-2021:1906

  • libyang AlmaLinux 8 1.0.184-1.el8

almalinux advisories ALEA-2021:1906

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-20398 updated cvss 5.5

libyang: NULL pointer dereference in function lys_extension_instances_free()

  • Red Hat Enterprise Linux AppStream (v. 8) libyang 1.0.184-1.el8
    fixed: vendor fix RHEA-2021:1906

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.82% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/CESNET/libyang/issues/773 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.