Integer overflow in Openwrt
CVE-2026-55490
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (50.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 50.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Openwrt — versions < 25.12.5
Weakness classification (CWE)
References
- github.com/openwrt/openwrt/security/advisories/GHSA-9558-77jp-g3fw (Exploit, Vendor Advisory)
- github.com/openwrt/openwrt/commit/63c0767f3d02f7b10b0f0b5293366bd059a08ca5 (Patch)
- github.com/openwrt/openwrt/releases/tag/v25.12.5 (Release Notes)
Frequently asked questions
- What is CVE-2026-55490?
- CVE-2026-55490 is a medium-severity vulnerability in Openwrt, classified under Integer Underflow. CVSS score: 6.5/10. Published 2026-07-07.
- How severe is CVE-2026-55490?
- Medium severity. CVSS v3 base score is 6.5 out of 10.