CVE-2025-6599 — Uncontrolled Resource Consumption in Zyxel Ax7501-b0 Firmware

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Zyxel Ax7501-b0 Firmware, Zyxel Ax7501-b1 Firmware, Zyxel Dm4200-b0 Firmware…).
2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
4. Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-400 · Uncontrolled Resource Consumption

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.31%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
• Track CPU/memory spikes and availability drops correlated with request patterns.

Timeline

What happened to this CVE, newest first.

• 2026
• Affected products added · zyxel/dx3301-t0 firmware
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• CVSS changed · 7.5
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Analyzed
  Oct 13, 2026 · NIST National Vulnerability Database
• Record created in this database
  Oct 13, 2026 · NIST National Vulnerability Database
• 2025
• CVE published
  Nov 17, 2025 · Zyxel

Source activity

Repeated readings are counted rather than listed.

• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

• www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-unc
  Vendor Advisory, vendor-advisory, NIST National Vulnerability Database

Elsewhere on this site

Related CVEs (same products)

• High CVE-2026-1460 OS Command Injection in Zyxel Nebula Fwa70 Firmware Apr 28, 2026
• Medium CVE-2026-0711 OS Command Injection in Zyxel Nr5307 Firmware Apr 28, 2026
• Critical CVE-2025-13942 OS Command Injection in Zyxel Wx5610-b0 Firmware Feb 24, 2026
• Medium CVE-2025-11848 NULL Pointer Dereference in Zyxel Ex5601-t1 Firmware Feb 24, 2026
• High CVE-2025-13943 OS Command Injection in Zyxel Ex5601-t1 Firmware Feb 24, 2026
• High CVE-2026-1459 OS Command Injection in Zyxel Vmg3625-t50c Firmware Feb 24, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No fixed version, patch or mitigation documented.
• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-6599 is "Uncontrolled Resource Consumption in Zyxel Ax7501-b0 Firmware", rated High. It affects Ax7501-b0 Firmware (Zyxel); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.31% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.

Sign in or create an account to comment and suggest corrections.