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CRITICAL severity

CVE-2026-123957

CRITICAL

CVE-2026-123957 is a critical-severity (CVSS 9.9) Buffer Overflow vulnerability. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

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…

Published
Updated
Affected
—
Patched
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Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Description

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.

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    The records we use list no fixed release for CVE-2026-123957. Check the upstream advisory for a patched version, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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