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CVE-2026-55731— Loytec LINX firmware: Unchecked input for loop condition in the SNMP agent

Quick assessment

Affected
Loytec LIP-ME20xC
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.

LOYTEC LIP-ME20xC是LOYTEC公司的一款工业路由器。 LOYTEC LIP-ME20xC、L-INX、L-GATE、L-ROC、L-IOB、L-DALI、L-VIS和L-PAD 8.4.16及之前版本存在输入验证错误漏洞，该漏洞源于SNMP代理中循环条件的输入未经检查，可能导致未经身份验证的远程攻击者通过特制的SNMP GETNEXT请求（带有大OID组件）造成持久拒绝服务（CPU耗尽）。

CVSS 6.6 · Medium EPSS 0.32% · P25

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 8

VendorProduct Version RangeStatus
Loytec L-DALI ≤ 8.4.16 affected
Loytec L-GATE ≤ 8.4.16 affected
Loytec L-INX ≤ 8.4.16 affected
Loytec L-IOB ≤ 8.4.16 affected
Loytec L-PAD ≤ 8.4.16 affected
Loytec L-ROC ≤ 8.4.16 affected
Loytec L-VIS ≤ 8.4.16 affected
Loytec LIP-ME20xC ≤ 8.4.16 affected
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I. Basic Information for CVE-2026-55731

Vulnerability Information
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Vulnerability Title
Loytec LINX firmware: Unchecked input for loop condition in the SNMP agent
Source: CVE Program / CVE List V5
Vulnerability Description
Unchecked input for loop condition (CWE-606) in the SNMP agent in Loytec LIP-ME201C, L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS and L-PAD through 8.4.16 on LINX-A64 allows an unauthenticated remote attacker to cause persistent denial of service (CPU exhaustion) via a crafted SNMP GETNEXT request with a large OID component.
Source: CVE Program / CVE List V5
CVSS Information
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:U
Source: CVE Program / CVE List V5
Vulnerability Type
循环条件输入未经检查
Source: CVE Program / CVE List V5
Vulnerability Title
LOYTEC LIP-ME20xC 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
LOYTEC LIP-ME20xC是LOYTEC公司的一款工业路由器。 LOYTEC LIP-ME20xC、L-INX、L-GATE、L-ROC、L-IOB、L-DALI、L-VIS和L-PAD 8.4.16及之前版本存在输入验证错误漏洞，该漏洞源于SNMP代理中循环条件的输入未经检查，可能导致未经身份验证的远程攻击者通过特制的SNMP GETNEXT请求（带有大OID组件）造成持久拒绝服务（CPU耗尽）。
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
Loytec LIP-ME20xC 0 ~ 8.4.16 -
Loytec L-INX 0 ~ 8.4.16 -
Loytec L-GATE 0 ~ 8.4.16 -
Loytec L-ROC 0 ~ 8.4.16 -
Loytec L-IOB 0 ~ 8.4.16 -
Loytec L-DALI 0 ~ 8.4.16 -
Loytec L-VIS 0 ~ 8.4.16 -
Loytec L-PAD 0 ~ 8.4.16 -

II. Public POCs for CVE-2026-55731

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III. Intelligence Information for CVE-2026-55731

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Vendor Advisories for CVE-2026-55731 (1)

Same Patch Batch · Loytec · 2026-07-24 · 9 CVEs total

CVE-2026-12503 9.2 CRITICAL Loytec LINX firmware: Improper Link Resolution in /usr/bin/larm_starter
CVE-2026-12496 8.7 HIGH Loytec LINX firmware: Unauthenticated stored XSS in OPC XML-DA server
CVE-2026-55730 8.7 HIGH Loytec LWEB802: Reflected Cross-Site Scripting in LWEB802
CVE-2026-55732 8.7 HIGH Loytec LINX firmware: Out-of-bounds Read in BACnet packet parsing (bacdt_datetime_to_tod)
CVE-2026-12502 8.4 HIGH Loytec LINX firmware: Improper Privilege Management in /usr/bin/ltsudo
CVE-2026-12504 8.4 HIGH Loytec LINX firmware: Improper Authentication in PAM configuration
CVE-2026-55729 7.7 HIGH Loytec LWEB802: Exposure of Sensitive Information in browser localStorage
CVE-2026-55728 3.8 LOW Loytec LINX firmware: Stack-based Buffer Overflow in cmd_ipaddr_conflict

IV. Related Vulnerabilities

Same product: LIP-ME20xC
Same vendor: Loytec
Same weakness: CWE-606

V. Comments for CVE-2026-55731

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