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CVE-2021-27861— L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths

Quick assessment

Affected
IEEE 802.2
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.

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AI Predicted 7.5 Difficulty: Moderate EPSS 0.66% · P50
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I. Basic Information for CVE-2021-27861

Vulnerability Information
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Vulnerability Title
L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths
Source: CVE Program / CVE List V5
Vulnerability Description
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
长度参数不一致性处理不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
多款Cisco产品安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Cisco NX-OS Software等都是美国思科（Cisco）公司的产品。Cisco NX-OS Software是一套交换机使用的数据中心级操作系统软件。Cisco IOS是一套为其网络设备开发的操作系统。Cisco IOS XE Software是一个操作系统。 Cisco IOS Software - Switches、Cisco IOS XE Software - Switches、Cisco IOS XE Software - Routers、Cisco IOS XR Software、C
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
IEEE 802.2 802.2h-1997 ~ 802.2h-1997 -
IETF draft-ietf-v6ops-ra-guard 08 ~ 08 -
IETF P802.1Q D1.0 ~ D1.0 -

II. Public POCs for CVE-2021-27861

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III. Intelligence Information for CVE-2021-27861

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Vendor Advisories for CVE-2021-27861 (1)

Security Blog Posts for CVE-2021-27861 (1)

Other References for CVE-2021-27861 (3)

Same Patch Batch · IEEE · 2022-09-27 · 3 CVEs total

CVE-2021-27853 L2 network filtering can be bypassed using stacked VLAN0 and LLC/SNAP headers
CVE-2021-27862 L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with an invalid lengt

IV. Related Vulnerabilities

Same product: 802.2
Same vendor: IEEE
Same weakness: CWE-130

V. Comments for CVE-2021-27861

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