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CVE-2019-20398

21
FAUCET Score

CVE-2019-20398 is a NULL pointer dereference vulnerability affecting libyang versions prior to v1.0-r3, specifically within the lys_extension_instances_free() function when handling unresolved extensions. This flaw can lead to application crashes when parsing untrusted YANG files. Rated Medium severity (CVSS 6.5), it requires user interaction (UI:R) and network access (AV:N) to exploit, resulting in high availability impact (A:H). There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
0.11CPE matchmatch criteria
cpe:2.3:a:cesnet:libyang:0.11:r1:*:*:*:*:*:*
0.11CPE matchmatch criteria
cpe:2.3:a:cesnet:libyang:0.11:r2:*:*:*:*:*:*
0.12CPE matchmatch criteria
cpe:2.3:a:cesnet:libyang:0.12:r1:*:*:*:*:*:*
0.12CPE matchmatch criteria
cpe:2.3:a:cesnet:libyang:0.12:r2:*:*:*:*:*:*
0.13CPE matchmatch criteria
cpe:2.3:a:cesnet:libyang:0.13:r1:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.82%
Probability of exploitation in next 30 days
EPSS Percentile
76.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0182 is in the 88th percentile among its peer group of 26,234 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: libyang-0:1.0.184-1.el8
View patch

Vendor Advisories (1)

redhatCVE-2019-20398Low

libyang: NULL pointer dereference in function lys_extension_instances_free()

Apr 29, 2019

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
github.com / CESNET/libyang/commit/7852b272ef77f8098c35deea6c6f09cb78176f08
Patch
github.com / CESNET/libyang/compare/v1.0-r2...v1.0-r3
Third Party Advisory
github.com / CESNET/libyang/issues/773
ExploitThird Party Advisory
lists.debian.org / debian-lts-announce/2023/09/msg00019.html