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CVE-2026-80303— Avast WFP stream parser integer underflow causes system crash

Quick assessment

Affected
Gen Digital Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Avast 在 Windows 过滤平台（WFP）的流解析器中存在一个整数下溢漏洞，攻击者可利用该漏洞通过引发系统崩溃来实施拒绝服务（DoS）攻击。 WFP 调用驱动程序负责处理网络流数据，并计算用于数据包分片重组的长度值。该长度计算过程未对输入流大小与预期边界进行充分验证。当处理特制的输入数据时，长度计算会发生下溢，导致系统以异常巨大的回绕数值进行内存分配或缓冲区访问。 该下溢漏洞可通过以下两种方式触发：远程通过发往被过滤端口的网络流量，或本地通过向过滤接口提供特制数据。由此引发的内存分配失败或越界访问将导致内核

AI Predicted 7.5 Difficulty: Easy
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I. Basic Information for CVE-2026-80303

Vulnerability Information
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Vulnerability Title
Avast WFP stream parser integer underflow causes system crash
Source: CVE Program / CVE List V5
Vulnerability Description
An integer underflow vulnerability in the Avast Windows Filtering Platform (WFP) stream parser on Windows allows denial of service by causing a system crash. The WFP callout driver processes network stream data and computes length values for packet fragment reassembly. The length calculation does not properly validate input stream sizes against expected boundaries. When processing specially crafted input, the length computation underflows, resulting in allocation or buffer access with an extremely large wrapped-around size value. The underflow can be triggered remotely via network traffic destined for the filtered port, or locally via crafted data provided to the filtering interface. The resulting memory allocation failure or out-of-bounds access causes a kernel panic and system crash.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
整数下溢(超界折返)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Gen Digital Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate 0 ~ 26.7 -
Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate 0 ~ 26.7 -
Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced 0 ~ 26.7 -

II. Public POCs for CVE-2026-80303

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III. Intelligence Information for CVE-2026-80303

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Vendor Pages for CVE-2026-80303 (3)

Same Patch Batch · Gen Digital · 2026-11-06 · 4 CVEs total

CVE-2026-12067 AvastSvc denial of service via unhandled JsonCpp exceptions in native message handlers
CVE-2026-80302 Avast sandbox escape via arbitrary file write in virtualized environment
CVE-2026-80301 Avast sandbox escape via unpreserved COM pathway through Task Scheduler

IV. Related Vulnerabilities

Same product: Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate
Same vendor: Gen Digital
Same weakness: CWE-191