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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-5857 Detail

Description

Contiki-NG's MQTT client parse_publish_vhdr() in os/net/app-layer/mqtt/mqtt.c sets topic_len_received=1 before checking topic_len against the 64-byte limit, so an over-length topic returns early but leaves the flag set. On the next TCP segment, tcp_input() re-invokes the parser with topic_received==0, and the persisted topic_len_received==1 skips the length-reading block containing the guard, falling through directly to a memcpy() that uses the unvalidated 16-bit topic_len as the copy length. The 65-byte topic[] destination overruns into adjacent struct fields including the payload_chunk pointer, which subsequent MQTT code dereferences, giving a compromised or attacker-controlled broker an arbitrary-pointer-write primitive. Contiki-NG's MQTT implementation has no TLS support so the connection is plaintext. Impact ranges from information disclosure and denial of service to remote code execution on embedded targets without memory protection.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  VulnCheck
CVSS-B 9.2 CRITICAL
Vector:  CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/contiki-ng/contiki-ng VulnCheck
https://github.com/contiki-ng/contiki-ng/commit/a34a2dbdc8bea784bd2ae5079aa4be520cd74f2d VulnCheck
https://github.com/contiki-ng/contiki-ng/pull/3163 VulnCheck

Weakness Enumeration

CWE-ID CWE Name Source
CWE-787 Out-of-bounds Write VulnCheck  

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-5857
NVD Published Date:
08/06/2026
NVD Last Modified:
08/06/2026
Source:
VulnCheck