CVE-2026-74221Network attack vector

Bootloader crash via unchecked NFS symlink length

Published Sep 29, 2026 · Updated Sep 29, 2026

Buffer overflow in U-Boot before 2026.10-rc5 allows remote attackers controlling an NFS server to crash the bootloader via crafted READLINK replies. The nfs_readlink_reply() parser accepts negative or oversized symlink lengths without adequate bounds validation before copying response data into a path buffer. Exposure requires an NFS network boot that accepts the malicious server's replies; code execution is not established for this CVE.

CVSS severityUnavailable
Unscored
EPSS probability0.34%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in U-Boot before 2026.10-rc5 allows remote attackers controlling an NFS server to crash the bootloader via crafted READLINK replies. The nfs_readlink_reply() parser accepts negative or oversized symlink lengths without adequate bounds validation before copying response data into a path buffer. Exposure requires an NFS network boot that accepts the malicious server's replies; code execution is not established for this CVE.

The record

CVE
CVE-2026-74221
Published
Sep 29, 2026
Updated
Sep 29, 2026
Vendor
DENX Software Engineering GmbH
Product
U-Boot
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 29, 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 <2026.10-rc5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

DENX Software Engineering GmbH · U-Bootversion=0 <2026.10-rc5

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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