libyang before 5.2.6 contains a heap use-after-free write vulnerability in lyd_parser_set_data_flags that incorrectly updates metadata list pointers when freeing non-head default metadata entries. Attackers can trigger this vulnerability by submitting crafted YANG XML documents with specific metadata attributes to applications parsing untrusted XML data, causing process crashes or potential code execution.
https://www.vulncheck.com/advisories/libyang-heap-use-after-free-write-in-xml-metadata-parsing
https://red.anthropic.com/2026/cvd/findings/ANT-2026-TZQ1KH7E
https://github.com/CESNET/libyang/security/advisories/GHSA-9f49-8x56-jmjc
https://github.com/CESNET/libyang/commit/6b5ed47ee674fbe86b31bbebc4ff26889aeff38c
Published: 2026-05-26
Updated: 2026-05-26
Base Score: 6.8
Vector: CVSS2#AV:N/AC:L/Au:S/C:N/I:N/A:C
Severity: Medium
Base Score: 6.5
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity: Medium
Base Score: 7.1
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Severity: High
EPSS: 0.00031