CVE-2019-20398 — A NULL pointer dereference is present in libyang before v1

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.

01What is this vulnerability?

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.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-01-22T00:00:00.000Z
• Last modified: 2024-08-05T02:39:09.444Z

09References

• github.com — https://github.com/CESNET/libyang/compare/v1.0-r2...v1.0-r3
• github.com — https://github.com/CESNET/libyang/commit/7852b272ef77f8098c35deea6c6f09cb78176f0…
• github.com — https://github.com/CESNET/libyang/issues/773
• bugzilla.redhat.com — https://bugzilla.redhat.com/show_bug.cgi?id=1793935
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2023/09/msg00019.html