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

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linksys / E5600: 1.1.0.26 (affected). Source: CNA: VulDB

## Severity and prioritization

- CVSS 4.0: 8.7 (high); 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:P; source: CNA: VulDB

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:X/RC:C; source: CNA: VulDB

- CVSS 3.0: 7.5 (high); CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:X/RC:C; source: CNA: VulDB

- CVSS 2.0: 7.8 (high); AV:N/AC:L/Au:N/C:N/I:N/A:C/E:POC/RL:ND/RC:C; source: CNA: VulDB

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-787, CWE-119

## Exploit evidence

- exploit: https://github.com/Zimo-666/E5600-cves/tree/main/04-upload-fw-multipart-overflow (CNA: VulDB)

## References

- https://vuldb.com/vuln/430465 (CNA: VulDB; vdb-entry, technical-description)

- https://vuldb.com/vuln/430465/cti (CNA: VulDB; signature, permissions-required)

- https://vuldb.com/cve/CVE-2026-121617 (CNA: VulDB; third-party-advisory)

- https://vuldb.com/submit/1023313 (CNA: VulDB; third-party-advisory)

- https://github.com/Zimo-666/E5600-cves/tree/main/04-upload-fw-multipart-overflow (CNA: VulDB; exploit)

- https://www.linksys.com/ (CNA: VulDB; product)

## Provenance

- CNA: VulDB: https://www.cve.org/CVERecord?id=CVE-2026-121617; retrieved 2026-11-04; source updated 2026-11-04

Revision: 5bd445829e0514842f0f43e1ad5c1591e59ce9ea80d22d6773f74517411eb85c

Canonical: https://y2.dev/cve/CVE-2026-121617

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