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lwIP CVE-2026-91018

| EUVDEUVD-2026-84864 HIGH
Double Free (CWE-415)
2026-09-22 icscert GHSA-rmx4-24pf-8x6h
8.7
CVSS 4.0 · Vendor: icscert
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Severity by source

Vendor (icscert) PRIMARY
8.7 HIGH
CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
8.8 HIGH

Adjacent-network reachable double free with no auth or interaction (AV:A/AC:L/PR:N/UI:N); crash-to-code-exec spread justifies high C/I/A, though A:H is the most reliable impact.

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

Primary rating from Vendor (icscert).

CVSS VectorVendor: icscert

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

5
Analysis Updated
Sep 22, 2026 - 21:28 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Sep 22, 2026 - 21:22 vuln.today
cvss_changed
CVSS changed
Sep 22, 2026 - 21:22 NVD
8.8 (HIGH) 8.7 (HIGH)
Analysis Generated
Sep 22, 2026 - 21:02 vuln.today
CVE Published
Sep 22, 2026 - 20:25 cve.org
HIGH 8.8

DescriptionCVE.org

lwIP (Lightweight IP) has a double free vulnerability, which could crash the system, cause a DoS, memory corruption, or allow code execution on the victim system.

AnalysisAI

Double-free memory corruption in the lwIP (Lightweight IP) stack's API layer lets an unauthenticated attacker on an adjacent network segment crash or corrupt memory on embedded devices and firmware that link lwIP, with confidentiality, integrity, and availability all assessed as high impact (CVSS 4.0 base 8.7; independent assessment CVSS 3.1 AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H). The attack requires the attacker to already sit on the same or an adjacent L2 segment rather than the open internet, but needs no credentials or user interaction; successful exploitation can cause a denial of service and, depending on the target's heap hardening and allocator behavior, may extend to code execution, though reliable RCE on embedded targets is constrained by the difficulty of exploiting double-free conditions. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Impact
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Vulnerability AssessmentAI

Exploitation Requires adjacent-network access (CVSS AV:A) - the attacker must reach the device on the local or an adjacent L2 segment, not across the open internet - targeting a device whose firmware links the lwIP TCP/IP stack and exercises the vulnerable double-free code path via network input. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The only quantified signal is the vendor's CVSS 4.0 base score of 8.7 (AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H), which describes an unauthenticated, low-complexity attack requiring adjacent-network access (AV:A) with high impact to confidentiality, integrity, and availability. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation No vendor-released patch identified at time of analysis, and no fixed version number appears in the referenced sources, so remediation must currently be compensating rather than corrective. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory all embedded devices and firmware that link the lwIP stack, identify any exposed to adjacent L2/L3 segments, and apply immediate network access controls such as ACLs, VLAN segmentation, and firewall rules to prevent unauthenticated adjacent-network access; disable unnecessary lwIP-based services and monitor for abnormal crashes or memory-related failures. …

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CVE-2026-91018 vulnerability details – vuln.today

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