← Vulnerability feed

Vulnerability record · CVE-2020-25108 · published 11 December 2020

CVE-2020-25108: Ethernut Nut/OS DNS response length flaw allows out-of-bounds write

Ethernut · Nut\/Os

The DNS implementation in Ethernut Nut/OS 5.1 does not validate the length field of DNS response data, so a packet can set an arbitrary length. This out-of-bounds write can cause a denial of service and possibly remote code execution.

9.8 CVSS 3.1 Critical EPSS 54% · top 1.0% CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score, v2 7.5
54%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

An issue was discovered in the DNS implementation in Ethernut in Nut/OS 5.1. The DNS response data length is not checked (it can be set to an arbitrary value from a packet). This may lead to successful Denial-of-Service, and possibly Remote Code Execution.

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

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 20 September 2026. Confidence: medium.

critical priorityCVSS 9.8 with network reachability, no authentication, and high EPSS make this a critical exposure despite no confirmed in-the-wild exploitation.

What it is

The DNS implementation in Ethernut Nut/OS 5.1 does not validate the length field of DNS response data, so a packet can set an arbitrary length. This out-of-bounds write can cause a denial of service and possibly remote code execution.

Impact

An attacker can crash or destabilize the device via malformed DNS responses, and the out-of-bounds write may allow remote code execution in the context of the affected service.

Attack surface

Reachable over the network via DNS response packets (CVSS AV:N, AC:L, PR:N, UI:N), so no authentication or user interaction is required. Any device running Nut/OS 5.1 that processes DNS responses is exposed.

Exploitation

Not listed in CISA KEV and no public exploit references are provided, but EPSS is 0.53699 (99th percentile), indicating a high predicted likelihood of exploitation activity.

What to do

  • Apply the vendor fix or update Nut/OS beyond 5.1 if available; consult the CISA ICS advisory ICSA-20-343-01 for vendor guidance.
  • If patching is not possible, restrict DNS traffic to trusted resolvers and segment affected devices from untrusted networks.
  • Disable or avoid DNS resolution on affected devices where the function is not required.
  • Monitor vendor and CERT/CC advisories for updated remediation guidance.

Detection

  • Monitor device logs for crashes, reboots, or abnormal resets correlated with DNS traffic.
  • Inspect network traffic for DNS responses with anomalous or oversized length fields.
  • Watch for unexpected process termination or memory corruption indicators on Nut/OS devices.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://us-cert.cisa.gov/ics/advisories/icsa-20-343-01 Third Party AdvisoryUS Government Resource
https://www.kb.cert.org/vuls/id/815128 Third Party AdvisoryUS Government Resource
https://us-cert.cisa.gov/ics/advisories/icsa-20-343-01 Third Party AdvisoryUS Government Resource
https://www.kb.cert.org/vuls/id/815128 Third Party AdvisoryUS Government Resource

Track CVE-2020-25108 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2020-25107Nut/OS DNS resolver missing null-termination check allows DoS and possible RCEThe DNS implementation in Ethernut Nut/OS 5.1 does not verify that a domain name is '\0' terminated, an out-of-bounds read condition. A malformed DNS…EPSS 54%analysed9.8CVE-2020-25109Ethernut Nut/OS DNS header count out-of-bounds readThe DNS implementation in Ethernut Nut/OS 5.1 does not validate the query/response count in the DNS header against the actual data present, causing a…EPSS 54%analysed9.8CVE-2020-25110Ethernut Nut/OS DNS length byte flaw allows denial of service and possible RCEThe DNS implementation in Ethernut Nut/OS 5.1 fails to validate the length byte of a domain name in DNS queries and responses, then uses that value f…EPSS 54%analysed7.5CVE-2020-27213Ethernut nut\/os vulnerabilityAn issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an i…EPSS 0.97%8.8CVE-2026-53266Linux kernel ebtables SNAT out-of-bounds write in ARP rewriteThe ebtables SNAT target rewrites the ARP sender hardware address via skb_store_bits() without first making that range writable. When the ARP SHA byt…KEVEPSS 0.65%analysed8.8CVE-2026-87491Google Chrome V8 out-of-bounds write enables sandbox code executionChrome before 153.0.8010.36 contains an out-of-bounds write in the V8 JavaScript engine. A crafted HTML page can trigger the memory corruption, and b…KEVEPSS 3.1%analysed9.8CVE-2025-25249Fortinet FortiOS and FortiSwitchManager heap buffer overflow via crafted packetsA heap-based buffer overflow (CWE-122/CWE-787) in Fortinet FortiOS 6.4 through 7.6.3 and FortiSwitchManager 7.0 through 7.2.6 lets an unauthenticated…KEVEPSS 3.9%analysed7.8CVE-2026-53362Linux kernel IPv6 UDP paged allocation out-of-bounds write__ip6_append_data() in the Linux kernel mis-accounts fraggap on the paged-allocation path, leaving the linear skb area undersized while pagedlen is o…KEVEPSS 0.71%analysed

Source: NIST National Vulnerability Database (record CVE-2020-25108), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.