Is CVE-2026-121616 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-121616 being exploited in the wild.

How severe is CVE-2026-121616?

Medium severity, with a CVSS score of 5.3, published 4 November 2026.

Is there a fix for CVE-2026-121616?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-121616 attacked?

It is attacked over the network, in device firmware.

Am I affected by CVE-2026-121616?

Check whether you run Linksys E5600 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-121616: Linksys E5600 buffer overflow in mesh_login.cgi

CVE-2026-121616 · Severity: medium · CVSS 5.3 · Published 2026-11-04

The Linksys E5600 router firmware contains a buffer overflow vulnerability in the JSON parser for the mesh login endpoint. An unauthenticated attacker can send a specially crafted request that overwrites security-relevant memory, potentially leading to authentication bypass or denial of service. This affects only end-of-life firmware versions that are no longer supported.

Technologies: Linksys E5600. Vendors: Linksys.

Quick answers

Is CVE-2026-121616 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-121616 being exploited in the wild.
How severe is CVE-2026-121616?: Medium severity, with a CVSS score of 5.3, published 4 November 2026.
Which products and versions are affected?: Linksys E5600 1.1.0.26.
Is there a fix for CVE-2026-121616?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-121616 attacked?: It is attacked over the network, in device firmware.
Am I affected by CVE-2026-121616?: Check whether you run Linksys E5600 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The JSON request parser in /cgi-bin/mesh_login.cgi uses unbounded strcpy() to copy attacker-controlled fields (username, password, token, source, cn, action) into fixed-size global buffers, resulting in an out-of-bounds write (CWE-787/CWE-120). The vulnerability is reachable without authentication and can corrupt adjacent global variables in the .bss segment that store login state and credentials. Exploitation is publicly available but impact is constrained by memory layout variations across devices.

Affected products

Linksys E5600 1.1.0.26

Timeline

2026-11-04: disclosed: Public disclosure via GitHub repository

References

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