Out-of-Bounds Write Vulnerability in Linksys E5600 by Cisco
CVE-2026-121617

8.7HIGH

Key Information:

Vendor

Linksys
Status
E5600
Vendor
CVE Published:
4 November 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-121617?

A security flaw has been identified in Linksys E5600 firmware version 1.1.0.26, specifically in the init_multipart function of the /cgi-bin/upload_fw.cgi component. This vulnerability allows for out-of-bounds write operations that can be exploited remotely. The issue affects products that are no longer supported by the vendor, and an exploit has been publicly disclosed, increasing the risk for devices that remain vulnerable. The vendor has not provided a response regarding this disclosure.

Affected Version(s)

E5600 1.1.0.26

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-121617 - Proof of Concept

References

https://vuldb.com/vuln/430465
vdb-entrytechnical-description
https://vuldb.com/vuln/430465/cti
signaturepermissions-required
https://vuldb.com/cve/CVE-2026-121617
third-party-advisory

CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

liuyingqi (VulDB User)
VulDB CNA Team
.