NVD / CVE Program· CNA f5

CVE-2021-23053: On version 15.1.x before 15.1.3, 14.1.x before 14.1.3.1, and 13.1.x before 13.1.3.6, when the brute force protection feature of BIG-IP…

MediumCVSS 5.3 · v3.1—No exploit No fix recorded

Noroxi assessment

Priority: Monitor (action score 21/100)

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: 0.91% (FIRST EPSS); higher than 60.6% of all records.
Anyone who can reach it over the internet 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

On version 15.1.x before 15.1.3, 14.1.x before 14.1.3.1, and 13.1.x before 13.1.3.6, when the brute force protection feature of BIG-IP Advanced WAF or BIG-IP ASM is enabled on a virtual server and the virtual server is under brute force attack, the MySQL database may run out of disk space due to lack of row limit on undisclosed tables in the MYSQL database. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Published: Sep 14, 2021
Updated: Jun 16, 2026
EPSS: 0.9% · 60th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 21 / 40 · 5.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.9%

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.

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.

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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.

Vendor	Product	CPE
f5	big-ip advanced web application firewall	cpe:2.3:a:f5:big-ip_advanced_web_application_firewall
f5	big-ip application security manager	cpe:2.3:a:f5:big-ip_application_security_manager

Affected versions

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

f5 big-ip advanced web application firewall13.1.0 and later · before 13.1.3.6
f5 big-ip advanced web application firewall14.1.0 and later · before 14.1.3.1
f5 big-ip advanced web application firewall15.1.0 and later · before 15.1.3
f5 big-ip application security manager13.1.0 and later · before 13.1.3.6
f5 big-ip application security manager14.1.0 and later · before 14.1.3.1
f5 big-ip application security manager15.1.0 and later · before 15.1.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (f5). Independent of NVD's CPE analysis and usually ahead of it.

n/a BIG-IP Advanced WAF and BIG-IP ASM
- 15.1.x before 15.1.3, 14.1.x before 14.1.3.1, and 13.1.x before 13.1.3.6affected

Same product

f5: all records

Other highest-scoring records for the same primary product.

CVE-2021-23031On version 16.0.x before 16.0.1.2, 15.1.x before 15.1.3, 14.1.x before 14.1.4.1, 13.1.x before 13.1.4, 12.1.x before 12.1.6, and 11.6.x…
40Plan
CVE-2021-23029On version 16.0.x before 16.0.1.2, insufficient permission checks may allow authenticated users with guest privileges to perform…
35Monitor
CVE-2021-23014On versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.3, and 14.1.x before 14.1.4, BIG-IP Advanced WAF and ASM are missing authorization…
35Monitor

Published before and after this one in the same product

← EarlierCVE-2021-22993Mar 31, 2021 · On BIG-IP Advanced WAF and BIG-IP ASM versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2, 14.1.x before 14.1.3.1, 13.1.x before…
35Monitor
← EarlierCVE-2021-23050Sep 14, 2021 · On BIG-IP Advanced WAF and BIG-IP ASM version 16.0.x before 16.0.1.2 and 15.1.x before 15.1.3 and NGINX App Protect on all versions before…
30Monitor
Later →CVE-2021-23033Sep 14, 2021 · On BIG-IP Advanced WAF and BIG-IP ASM version 16.x before 16.1.0x, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, 13.1.x before 13.1.4.1…
30Monitor

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

Anyone who can reach it over the internet 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: none
Integrity: none
Availability: low · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: Low

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-primary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

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

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

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

References

support.f5.com/csp/article/K36942191

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

All records