AUGUST 16, 2026
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Case File

CVE-2026-5856

HIGH · CVSS 7.1 EPSS 0.25% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-06 · Last synced 2026-08-16

CyberRota Analysis

AI-Generated

The vulnerability in Contiki-NG's DNS/mDNS resolver allows an attacker to exploit improper boundary checks in the skip_name() function, leading to out-of-bounds memory reads. This can result in the disclosure of sensitive memory contents or cause the resolver to crash, particularly affecting systems with multicast DNS support enabled. Organizations using Contiki-NG, especially those in IoT environments, should prioritize patching this vulnerability to mitigate potential data exposure and service disruptions.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-5856
Severity
HIGH
CVSS
7.1
EPSS
0.25%

Original NVD Description

Contiki-NG's DNS/mDNS resolver skip_name() in os/services/resolv/resolv.c walks DNS wire-format name labels with no packet-boundary check, and the caller in newdata() invokes it in a loop iterating nquestions times from the attacker-controlled DNS header before validating the transaction ID. An attacker who sets nquestions higher than the number of complete questions present causes skip_name() to walk past the UDP packet buffer, and the returned pointer is cast to struct dns_answer * for further memory reads. On builds with RESOLV_CONF_SUPPORTS_MDNS enabled, any peer on the local segment can trigger the read unauthenticated via a multicast UDP 5353 packet with no outstanding query required; on standard DNS builds an attacker who can inject a UDP response from port 53 during an outstanding query can trigger the same read. Impact is out-of-bounds read of uip_buf and adjacent memory, disclosing memory contents or crashing the resolver.