# CVE-2026-123957: TOTOLINK CA300-PoE cstecgi.cgi setIpQosRules buffer overflow

Status: published. Published: 2026-11-07. Updated: 2026-11-07.

A vulnerability was determined in TOTOLINK CA300-PoE 6.2c.884. Impacted is the function setIpQosRules of the file /cgi-bin/cstecgi.cgi. This manipulation of the argument ipStart causes buffer overflow. It is possible to initiate the attack remotely. The exploit has been publicly disclosed and may be utilized.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- TOTOLINK / CA300-PoE: 6.2c.884 (affected). Source: CNA: VulDB

## Severity and prioritization

- CVSS 4.0: 9.4 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P; source: CNA: VulDB

- CVSS 3.1: 9.9 (critical); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:X/RC:C; source: CNA: VulDB

- CVSS 3.0: 9.9 (critical); CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:X/RC:C; source: CNA: VulDB

- CVSS 2.0: 9 (critical); AV:N/AC:L/Au:S/C:C/I:C/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-120, CWE-119

## Exploit evidence

- exploit: https://lavender-bicycle-a5a.notion.site/TOTOLINK-CA300-PoE-setIpQosRules-3f953a41781f801195e5e07dfe7488b9?source=copy_link (CNA: VulDB)

## References

- https://vuldb.com/vuln/432020 (CNA: VulDB; vdb-entry, technical-description)

- https://vuldb.com/vuln/432020/cti (CNA: VulDB; signature, permissions-required)

- https://vuldb.com/cve/CVE-2026-123957 (CNA: VulDB; third-party-advisory)

- https://vuldb.com/submit/1033672 (CNA: VulDB; third-party-advisory)

- https://lavender-bicycle-a5a.notion.site/TOTOLINK-CA300-PoE-setIpQosRules-3f953a41781f801195e5e07dfe7488b9?source=copy_link (CNA: VulDB; exploit)

- https://www.totolink.net/ (CNA: VulDB; product)

## Provenance

- CNA: VulDB: https://www.cve.org/CVERecord?id=CVE-2026-123957; retrieved 2026-11-07; source updated 2026-11-07

Revision: c877ecf97210a314275b2ca16ef3a00aa24cf5aaa235bc682e6260f21aa83591

Canonical: https://y2.dev/cve/CVE-2026-123957

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