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VulnerabilityPublished Updated

CVE-2026-41401: libyang · Use After Free

Affects libyangSource CVE Database V5

0
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Public exploit available · CVSS 6.9 Medium : upgrade to 5.4.3 as a priority.

Data as of 29 Oct 2026, 21:45 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (VulnCheck)CVSS 4.06.9
CNA (VulnCheck)CVSS 3.16.5
CISA SSVC
Exploitation
Proof of concept is public or traded
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-05-26.

Patch
Available – fixed in 5.4.3
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

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 26 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CISA SSVC: proof of concept public

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by VulnCheck

    , 36 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. CISA SSVC assessment

    proof of concept public

    , 4 hours after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA SSVC, the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade libyang to 5.4.3.

Affected software

ProductAffectedFixed in
libyanglibyangAffected
  • <5.4.3
Fixed in
  • 5.4.3

AI-suggested

Upgrade libyang to version 5.4.3 or later, where this use-after-free vulnerability is fixed. No other mitigations are indicated or required according to the available data.

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.

References

Community reviews

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