Vulnerability · Published Jul 7, 2026 · Assigned by GitHub_M

CVE-2026-55490OpenWrt: EAD Integer Underflow → Pre-Auth Denial of Service

Medium 6.5

In plain English

A medium-severity security flaw in openwrt from openwrt. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.7%top 47.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
openwrt	openwrt	< 25.12.5

Weakness: CWE-191 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/openwrt/openwrt/security/advisories/GHSA-9558-77jp-g3fw x_refsource_CONFIRM
https://github.com/openwrt/openwrt/commit/63c0767f3d02f7b10b0f0b5293366bd059a08ca5 x_refsource_MISC
https://github.com/openwrt/openwrt/releases/tag/v25.12.5 x_refsource_MISC