CVE-2026-41401Public exploitNetwork attack vector

Process crash via freed metadata list node

Published May 26, 2026 · Updated May 26, 2026

Heap use-after-free in CESNET libyang before 5.4.3 allows remote authenticated users to crash XML-parsing applications. lyd_parser_set_data_flags replaces the caller's metadata-list pointer while freeing a non-head default entry, leaving a freed node reachable for a later write. Reachability requires attacker-controlled XML with specific YANG metadata attributes; a process crash is confirmed, while code execution depends on allocator behavior and heap layout.

CVSS severity6.9
Medium
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap use-after-free in CESNET libyang before 5.4.3 allows remote authenticated users to crash XML-parsing applications. lyd_parser_set_data_flags replaces the caller's metadata-list pointer while freeing a non-head default entry, leaving a freed node reachable for a later write. Reachability requires attacker-controlled XML with specific YANG metadata attributes; a process crash is confirmed, while code execution depends on allocator behavior and heap layout.

The record

CVE
CVE-2026-41401
Published
May 26, 2026
Updated
May 26, 2026
Vendor
CESNET
Product
libyang
Classifications
CWE-416
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 26, 2026CVE publishedPublication date reported by the CVE source.
  2. May 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.4.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

CESNET · libyangversion=0 <5.4.3

Published CVSS scores

6.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
6.5CESNETCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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