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Fedora 43: libcoap Major Security Flaw Identified 2025

Linuxsecurity •LinuxSecurity Advisories • December 5, 2025

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained networks in the Internet of Things. The protocol is designed for machine-to-machine (M2M) applications such as smart energy and building automation. libcoap implements a lightweight application-protocol for devices with constrained resources such as computing power, RF range, memory, bandwidth, or network packet sizes. This protocol, CoAP, was standardized in the IETF working group "CoRE" as RFC 7252. Update Information : Update to security release 4.3.5a

The Constrained Application Protocol (CoAP) is a specialized web transfer

protocol for use with constrained nodes and constrained networks in the Internet

of Things. The protocol is designed for machine-to-machine (M2M) applications

such as smart energy and building automation.

libcoap implements a lightweight application-protocol for devices with

constrained resources such as computing power, RF range, memory, bandwidth,

or network packet sizes. This protocol, CoAP, was standardized in the IETF

working group "CoRE" as RFC 7252.

Update to security release 4.3.5a

* Sat Nov 29 2025 Peter Robinson - 4.3.5a-1 - Update to 4.3.5a

[ 1 ] Bug #2388738 - CVE-2025-50518 libcoap: Libcoap Use-After-Free Vulnerability [fedora-41] [ 2 ] Bug #2388740 - CVE-2025-50518 libcoap: Libcoap Use-After-Free Vulnerability [fedora-42] [ 3 ] Bug #2416889 - CVE-2025-65493 libcoap: libcoap denial of service [fedora-41] [ 4 ] Bug #2416890 - CVE-2025-65494 libcoap: libcoap denial of service [fedora-41] [ 5 ] Bug #2416891 - CVE-2025-65493 libcoap: libcoap denial of service [fedora-42] [ 6 ] Bug #2416892 - CVE-2025-65495 libcoap: libcoap denial of service [fedora-41] [ 7 ] Bug #2416893 - CVE-2025-65493 libcoap: libcoap denial of service [fedora-43] ... Read the Full Advisory

This update can be installed with the "dnf" update program. Use su -c 'dnf upgrade --advisory FEDORA-2025-d408d76c4a' at the command line. For more information, refer to the dnf documentation available at

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

Major Security Flaw in libcoap Affecting IoT Devices A significant security flaw has been identified in libcoap, a library implementing the Constrained Application Protocol (CoAP) used in Internet of Things (IoT) applications. This vulnerability affects devices with constrained resources, such as those used in smart energy and building automation. Users of Fedora 43 are particularly impacted by this issue. 2 sources 25

Extracted Entities

Fedora 43: libcoap Major Security Flaw Identified 2025

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Extracted Entities

Attack Types (1)

CVEs (4)

Platforms (1)

Vulnerabilities (1)