Description
libyang before 5.4.3 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.
References6
- github.com/CESNET/libyang/commit/6b5ed47ee674fbe86b31bbebc4ff26…
- github.com/CESNET/libyang/security/advisories/GHSA-9f49-8x56-jm…
- red.anthropic.com/2026/cvd/findings/ANT-2026-TZQ1KH7E
- www.vulncheck.com/advisories/libyang-heap-use-after-free-write-…
- github.com/CESNET/libyang/security/advisories/GHSA-9f49-8x56-jm…
- red.anthropic.com/2026/cvd/findings/ANT-2026-TZQ1KH7E
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS 4.0
-
7.1
HIGH
Score source: CNA
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 1% percentile: 53 · as of 14 November 2026
- CWE
- CWE-416
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.