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CVE-2019-20396· NVD / CVE Program· CNA mitre

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

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.9% (FIRST EPSS); higher than 79.4% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: libyang (Debian:10) 0.16.105+really1.0-0+deb10u1; libyang (Debian:13) 1.0.176-1; libyang (Red Hat:enterprise_linux:8::appstream) 0:1.0.184-1.el8.

Low priority for now. Upgrade to libyang (Debian:10) 0.16.105+really1.0-0+deb10u1; libyang (Debian:13) 1.0.176-1; libyang (Red Hat:enterprise_linux:8::appstream) 0:1.0.184-1.el8 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

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.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Jan 22, 2020
Updated
Jun 16, 2026
EPSS
1.9% · 79th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.9%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
cesnetlibyang

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • cesnet libyang0.11
  • cesnet libyang0.12
  • cesnet libyang0.13
  • cesnet libyang0.14
  • cesnet libyang0.15
  • cesnet libyang0.16

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:10libyangbefore 0.16.105+really1.0-0+deb10u10.16.105+really1.0-0+deb10u1
Debian:13libyangbefore 1.0.176-11.0.176-1
Red Hat:enterprise_linux:8::appstreamlibyangbefore 0:1.0.184-1.el80:1.0.184-1.el8
Red Hat:enterprise_linux:8::appstreamlibyang-cpp-debuginfobefore 0:1.0.184-1.el80:1.0.184-1.el8
Red Hat:enterprise_linux:8::appstreamlibyang-debuginfobefore 0:1.0.184-1.el80:1.0.184-1.el8
Red Hat:enterprise_linux:8::appstreamlibyang-debugsourcebefore 0:1.0.184-1.el80:1.0.184-1.el8
Red Hat:enterprise_linux:8::appstreampython3-libyang-debuginfobefore 0:1.0.184-1.el80:1.0.184-1.el8

Same product

cesnet: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-19334In all versions of libyang before 1.0-r5, a stack-based buffer overflow was discovered in the way libyang parses YANG files with a leaf of t
    40Plan
  • CVE-2019-19333In all versions of libyang before 1.0-r5, a stack-based buffer overflow was discovered in the way libyang parses YANG files with a leaf of t
    40Plan
  • CVE-2019-20397A double-free is present in libyang before v1.0-r1 in the function yyparse() when an organization field is not terminated.
    36Monitor
  • CVE-2019-20394A double-free is present in libyang before v1.0-r3 in the function yyparse() when a type statement in used in a notification statement.
    36Monitor
  • CVE-2019-20393A double-free is present in libyang before v1.0-r1 in the function yyparse() when an empty description is used.
    36Monitor
  • CVE-2021-28903A stack overflow in libyang <= v1.0.225 can cause a denial of service through function lyxml_parse_mem().
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:libyang1.0.176-1 · Debian:13Package registry (OSV)
red hat:libyang0:1.0.184-1.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libyang-cpp-debuginfo0:1.0.184-1.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libyang-debuginfo0:1.0.184-1.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libyang-debugsource0:1.0.184-1.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:python3-libyang-debuginfo0:1.0.184-1.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

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

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records