Skip to content
Noroxi
NVD / CVE Program· CNA Zyxel

CVE-2023-33011: A format string vulnerability in the Zyxel ATP series firmware versions 5.10 through 5.36 Patch 2, USG FLEX series firmware versions 5.00 th

Noroxi assessment

Priority: Monitor (action score 35/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.34% (FIRST EPSS).
  • Someone on the same network segment can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A format string vulnerability in the Zyxel ATP series firmware versions 5.10 through 5.36 Patch 2, USG FLEX series firmware versions 5.00 through 5.36 Patch 2, USG FLEX 50(W) series firmware versions 5.10 through 5.36 Patch 2, USG20(W)-VPN series firmware versions 5.10 through 5.36 Patch 2, and VPN series firmware versions 5.00 through 5.36 Patch 2, could allow an unauthenticated, LAN-based attacker to execute some OS commands by using a crafted PPPoE configuration on an affected device when the cloud management mode is enabled.

HighCVSS 8.8 · v3.1—No exploit No fix recorded
Published
Jul 17, 2023
Updated
Jun 17, 2026
EPSS
0.3% · 27th percentile

Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Zyxel
8.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2023-33011

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for zyxel records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
zyxelusg 2200-vpn firmware
zyxelusg 2200-vpn
zyxelusg flex 100 firmware
zyxelusg flex 100
zyxelusg flex 100w firmware
zyxelusg flex 100w
zyxelusg flex 200 firmware
zyxelusg flex 200
zyxelusg flex 50 firmware
zyxelusg flex 50
zyxelusg flex 500 firmware
zyxelusg flex 500

and 32 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • zyxel usg 20w-vpn firmware5.10 and later · before 5.37
  • zyxel usg 2200-vpn firmware5.00 and later · before 5.37
  • zyxel usg flex 100 firmware5.00 and later · before 5.37
  • zyxel usg flex 100w firmware5.00 and later · before 5.37
  • zyxel usg flex 200 firmware5.00 and later · before 5.37
  • zyxel usg flex 50 firmware5.00 and later · before 5.37
  • zyxel usg flex 500 firmware5.00 and later · before 5.37
  • zyxel usg flex 50w firmware5.00 and later · before 5.37
  • zyxel usg flex 700 firmware5.00 and later · before 5.37
  • zyxel zywall atp100 firmware5.10 and later · before 5.37
  • zyxel zywall atp100w firmware5.10 and later · before 5.37
  • zyxel zywall atp200 firmware5.10 and later · before 5.37
  • zyxel zywall atp500 firmware5.10 and later · before 5.37
  • zyxel zywall atp700 firmware5.10 and later · before 5.37
  • zyxel zywall atp800 firmware5.10 and later · before 5.37
  • zyxel zywall vpn 100 firmware5.00 and later · before 5.37
  • zyxel zywall vpn 300 firmware5.00 and later · before 5.37
  • zyxel zywall vpn 50 firmware5.00 and later · before 5.37
  • zyxel zywall vpn100 firmware5.00 and later · before 5.37
  • zyxel zywall vpn2s firmware5.00 and later · before 5.37

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Zyxel). Independent of NVD's CPE analysis and usually ahead of it.

  • Zyxel ATP series firmware

    • 5.10 through 5.36 Patch 2affected

  • Zyxel USG FLEX 50(W) series firmware

    • 5.10 through 5.36 Patch 2affected

  • Zyxel USG FLEX series firmware

    • 5.00 through 5.36 Patch 2affected

  • Zyxel USG20(W)-VPN series firmware

    • 5.10 through 5.36 Patch 2affected

  • Zyxel VPN series firmware

    • 5.00 through 5.36 Patch 2affected

Same product

zyxel: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-34139A command injection vulnerability in the Free Time WiFi hotspot feature of the Zyxel USG FLEX series firmware versions 4.50 through 5.36 Pat
    35Monitor
  • CVE-2023-28767The configuration parser fails to sanitize user-controlled input in the Zyxel ATP series firmware versions 5.10 through 5.36, USG FLEX serie
    35Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone on the same network segment can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Adjacent
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-134 · Use of Externally-Controlled Format String

CVSS vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records