CVE-2026-121617— Linksys E5600 Header upload_fw.cgi init_multipart out-of-bounds write

Quick assessment

Affected

Linksys E5600

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.

在 Linksys E5600 固件版本 1.1.0.26 中发现一个安全漏洞。该问题影响位于组件 Header Parser 中文件的函数。对该函数的恶意操纵会导致越界写入。攻击者可以远程发起攻击。利用代码已向公众发布，可能被用于实施攻击。我们曾尽早联系厂商通报此披露，但未得到任何回应。该漏洞仅影响已不再由维护者提供支持的產品。

CVSS 7.5 · High Updated Nov 04, 2026

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Get alerts for future matching vulnerabilities Log in to subscribe

Vulnerability Information

Have questions about the vulnerability? See if Shenlong's analysis helps!

View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title

Linksys E5600 Header upload_fw.cgi init_multipart out-of-bounds write

Source: CVE Program / CVE List V5

Vulnerability Description

A security flaw has been discovered in Linksys E5600 1.1.0.26. Affected by this issue is the function init_multipart of the file /cgi-bin/upload_fw.cgi of the component Header Parser. The manipulation results in out-of-bounds write. The attack may be launched remotely. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Source: CVE Program / CVE List V5

Vulnerability Type

跨界内存写

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
Linksys	E5600	1.1.0.26	`cpe:2.3:o:linksys:e5600_firmware::::::::`

II. Public POCs for CVE-2026-121617

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-121617

请登录查看更多情报信息。

Other References for CVE-2026-121617 (5)

https://github.com/Zimo-666/E5600-cves/tree/main/04-upload-fw-multipart-overflow exploit
https://vuldb.com/cve/CVE-2026-121617 third-party-advisory
https://vuldb.com/vuln/430465/cti signature permissions-required
https://vuldb.com/vuln/430465 vdb-entry technical-description
https://vuldb.com/submit/1023313 third-party-advisory

https://www.cve.org/CVERecord?id=CVE-2026-121617

Same Patch Batch · Linksys · 2026-11-04 · 4 CVEs total

CVE-2026-121615	10.0 CRITICAL	Linksys E5600 Login mesh_login.cgi improper authentication
CVE-2026-121616	5.3 MEDIUM	Linksys E5600 JSON Request mesh_login.cgi strcpy out-of-bounds write
CVE-2026-121618	5.3 MEDIUM	Linksys E5600 Factory Quality Control fqc.cgi information disclosure

IV. Related Vulnerabilities

Same product: E5600

Same vendor: Linksys

Same weakness: CWE-787