CVE-2026-55490

Received Received - Intake

Integer Underflow in OpenWrt Emergency Access Daemon

Publication date: 2026-07-07

Last updated on: 2026-07-07

Assigner: GitHub, Inc.

Description

OpenWrt is a Linux operating system targeting embedded devices. Before v25.12.5, an integer underflow in handle_send_a() of the Emergency Access Daemon allows any unauthenticated attacker on the local network to crash the daemon by sending a single crafted UDP packet. The message length underflows before a bounds check and is then passed to memcpy as a very large size. This issue is fixed v25.12.5.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-07-07

Last Modified

2026-07-07

Generated

2026-07-08

AI Q&A

2026-07-08

EPSS Evaluated

N/A

NVD

CVE-2026-55490

Affected Vendors & Products

Vendor	Product	Version / Range
openwrt	openwrt	to 25.12.5 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-191	The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

Attack-Flow Graph

Executive Summary

This vulnerability exists in OpenWrt, a Linux operating system for embedded devices. Before version 25.12.5, there is an integer underflow in the function handle_send_a() of the Emergency Access Daemon. An unauthenticated attacker on the local network can exploit this by sending a specially crafted UDP packet. The crafted packet causes the message length to underflow before a bounds check, resulting in a very large size being passed to the memcpy function, which crashes the daemon.

Impact Analysis

The vulnerability allows any unauthenticated attacker on the local network to crash the Emergency Access Daemon by sending a single crafted UDP packet. This results in a denial of service (DoS) condition, making the affected service unavailable.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade OpenWrt to version 25.12.5 or later, where the issue has been fixed.

Since the vulnerability allows unauthenticated local network attackers to crash the Emergency Access Daemon, restricting access to the local network or disabling the daemon until the update can be applied may reduce risk.

Hi! I’m here to help you understand CVE-2026-55490. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70