How severe is CVE-2019-20398?

CVE-2019-20398 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2019-20398 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-20398?

CVE-2019-20398 primarily affects Cesnet Libyang. In total, 13 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-20398?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-20398 published?

CVE-2019-20398 was published on 2020-01-22 and last updated on 2026-06-17.

CVE-2019-20398

CVE-2019-20398 is a medium-severity vulnerability in Cesnet Libyang with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Cesnet Libyang
Published: 2020-01-22
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2019-20398?: CVE-2019-20398 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2019-20398 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-20398?: CVE-2019-20398 primarily affects Cesnet Libyang. In total, 13 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-20398?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-20398 published?: CVE-2019-20398 was published on 2020-01-22 and last updated on 2026-06-17.

References

Affected products (13)

cpe:2.3:a:cesnet:libyang:0.11:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.11:r2:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.12:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.12:r2:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.13:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.13:r2:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.14:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.15:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.16:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.16:r2:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:0.16:r3:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:1.0:r1:*:*:*:*:*:*
cpe:2.3:a:cesnet:libyang:1.0:r2:*:*:*:*:*:*

More vulnerabilities in Cesnet Libyang

CVE-2019-19334 — Critical (CVSS 9.8): In all versions of libyang before 1.0-r5, a stack-based buffer overflow was discovered in the way libyang parses YANG…
CVE-2019-19333 — Critical (CVSS 9.8): In all versions of libyang before 1.0-r5, a stack-based buffer overflow was discovered in the way libyang parses YANG…
CVE-2019-20397 — High (CVSS 8.8): A double-free is present in libyang before v1.0-r1 in the function yyparse() when an organization field is not…
CVE-2019-20394 — High (CVSS 8.8): A double-free is present in libyang before v1.0-r3 in the function yyparse() when a type statement in used in a…
CVE-2019-20393 — High (CVSS 8.8): A double-free is present in libyang before v1.0-r1 in the function yyparse() when an empty description is used.…
CVE-2023-26917 — High (CVSS 7.5): libyang from v2.0.164 to v2.1.30 was discovered to contain a NULL pointer dereference via the function…

All CVEs affecting Cesnet Libyang →

Other CWE-476 (NULL Pointer Dereference) vulnerabilities

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CVE-2020-14500 — Critical (CVSS 10.0): Secomea GateManager all versions prior to 9.2c, An attacker can send a negative value and overwrite arbitrary data.
CVE-2010-2495 — Critical (CVSS 10.0): The pppol2tp_xmit function in drivers/net/pppol2tp.c in the L2TP implementation in the Linux kernel before 2.6.34 does…
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Browse all CWE-476 (NULL Pointer Dereference) vulnerabilities →