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OpenWrt CVE-2026-55490

| EUVDEUVD-2026-42110 MEDIUM
Integer Underflow (CWE-191)
2026-07-07 GitHub_M
Integer Overflow Denial Of Service Openwrt
6.5
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
6.5 MEDIUM
AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
6.5 MEDIUM

AV:A because exploitation requires local network adjacency; PR:N and AC:L since a single unauthenticated UDP packet suffices; A:H for daemon crash; C:N/I:N as no data is accessed or modified.

3.1 AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

3
Patch available
Jul 07, 2026 - 23:01 EUVD
Analysis Generated
Jul 07, 2026 - 22:09 vuln.today
CVE Published
Jul 07, 2026 - 21:08 cve.org
MEDIUM 6.5

DescriptionCVE.org

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.

AnalysisAI

Integer underflow in the OpenWrt Emergency Access Daemon crashes the daemon when any unauthenticated attacker on the local network sends a single crafted UDP packet to it. Affected are all OpenWrt versions prior to v25.12.5. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Gain adjacent network access (LAN/Wi-Fi)
Delivery
identify OpenWrt device running EAD
Exploit
craft UDP packet with underflowing length field
Execution
send single packet to EAD listening port
Persist
integer underflow passed to memcpy
Impact
daemon crash, EAD unavailable
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Vulnerability AssessmentAI

Exploitation The Emergency Access Daemon must be running and reachable on the target device (its default operational state on affected OpenWrt versions). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The NVD CVSS 3.1 base score of 6.5 (Medium) accurately reflects the constrained impact profile. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker positioned on the same local network segment as an unpatched OpenWrt device constructs a UDP packet with a message length field set so that the subtraction in handle_send_a() wraps to a very large unsigned integer. The attacker sends this single packet to the Emergency Access Daemon's listening UDP port; the daemon passes the underflowed length to memcpy, triggering a crash and making EAD unavailable. …
Remediation Upgrade to OpenWrt v25.12.5, which contains the confirmed fix per the upstream release at https://github.com/openwrt/openwrt/releases/tag/v25.12.5 and the patch commit at https://github.com/openwrt/openwrt/commit/63c0767f3d02f7b10b0f0b5293366bd059a08ca5. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-55490 vulnerability details – vuln.today
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