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Vulnerability record · CVE-2026-49494 · published 7 June 2026

CVE-2026-49494: Xcitium Client Security (XCS) before 13.8.2.10019 and Comodo Internet Security (CIS) through 12.3.4.8162 (fix …

Xcitium Client Security (XCS) before 13.8.2.10019 and Comodo Internet Security (CIS) through 12.3.4.8162 (fix expected by 2026 Q3) contain an integer underflow vulnerability in the firewall driver Inspect.sys that allows remote unauthenticated attackers to crash the system by sending a crafted IPv6 packet with a declared payload length smaller than the sum of its extension-header lengths. The unsigned 64-bit payload-length value underflows to a near-maximal integer, triggering an out-of-bounds read and oversized memcpy in the Windows kernel at DISPATCH_LEVEL, resulting in a blue screen of death even on hosts with all ports blocked.

8.7 CVSS 4.0 High EPSS 0.79% · top 45.4% CWE-191 · CWE-191 Deferred
8.7CVSS 4.0 base score
0.79%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
23 Jul 2026Last modified by NVD

Description

Xcitium Client Security (XCS) before 13.8.2.10019 and Comodo Internet Security (CIS) through 12.3.4.8162 (fix expected by 2026 Q3) contain an integer underflow vulnerability in the firewall driver Inspect.sys that allows remote unauthenticated attackers to crash the system by sending a crafted IPv6 packet with a declared payload length smaller than the sum of its extension-header lengths. The unsigned 64-bit payload-length value underflows to a near-maximal integer, triggering an out-of-bounds read and oversized memcpy in the Windows kernel at DISPATCH_LEVEL, resulting in a blue screen of death even on hosts with all ports blocked.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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:

References

LinkTags
https://github.com/MalwareTech/ComoDoS
https://malwaretech.com/2026/06/exploiting-a-remote-kernel-vulnerability-in-comodo-internet-security.html
https://updates.xcitium.com/#note11312
https://www.vulncheck.com/advisories/xcitium-client-security-comodo-internet-security-remote-dos

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-49494), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.