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VulnerabilityPublished

CVE-2026-120596: Ethernut / egnite Nut/Net TCP/IP Stack · Infinite Loop

Affects Ethernut / egnite Nut/Net TCP/IP StackSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High.

Data as of 2 Nov 2026, 17:43 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.17.5
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-02.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  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

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ethernut / egnite GmbHNut/Net TCP/IP StackAffected
  • =Nut/OS 5.1
Fixed in–

AI-suggested

Until a fix is available, network-level filtering to block malformed TCP segments with unknown options of zero length may mitigate exploitation. Rebooting the device restores normal operation after an attack.

Description

CVE-2026-120596 is a denial-of-service vulnerability in the Nut/Net TCP/IP stack used in Nut/OS by Ethernut/Egnite. The flaw allows an unauthenticated attacker to send a specially crafted TCP segment with an unknown TCP option length of zero, causing an infinite loop in the TCP options parser. This infinite loop blocks the TCP processing thread, making all TCP services on the device unresponsive until reboot. The vulnerability affects Nut/OS versions up to 5.1.

References

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