CVE-2026-53921

criticalpriority · track · 10EPSS 0.011 · 66 %ileexploit · PoCRU

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

2 exploits · PoC

Likely / severe?

1.12% (66th) EPSS

CVSS 9.8 · critical

Is it mine?

2 products

Check your exposure

Who says so?

1 sources

fstec_bdu

EPSS · scored 2026-10-27

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12.

cvss

Technical severity, 0–10. One row per scoring source.

9.8

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.19.8criticalAV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · security-advisories@github.comexploitability 3.9 · impact 5.9

v3.19.3criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Psecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-121USprimaryCWE-121US

exploits (2)

Public proof-of-concept and weaponised exploit code.

affected products (2)

Products and version ranges known to be affected.

also known as (2)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

fstec_bdu NVD CVE.org MITRE

published 2026-10-23modified 2026-10-23

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references (7) nvd

External citations — patches, advisories, analysis.

scry

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