NVD / CVE Program· CNA f5

CVE-2021-23049: On BIG-IP version 16.0.x before 16.0.1.2 and 15.1.x before 15.1.3, when the iRules RESOLVER::summarize command is used on a virtual server…

HighCVSS 7.5 · v3.1—No exploit No fix recorded

Noroxi assessment

Priority: Monitor (action score 30/100)

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: 0.96% (FIRST EPSS); higher than 62% 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 BIG-IP version 16.0.x before 16.0.1.2 and 15.1.x before 15.1.3, when the iRules RESOLVER::summarize command is used on a virtual server, undisclosed requests can cause an increase in Traffic Management Microkernel (TMM) memory utilization resulting in an out-of-memory condition and a denial-of-service (DoS). 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% · 62th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 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.

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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 access policy manager	cpe:2.3:a:f5:big-ip_access_policy_manager
f5	big-ip advanced firewall manager	cpe:2.3:a:f5:big-ip_advanced_firewall_manager
f5	big-ip advanced web application firewall	cpe:2.3:a:f5:big-ip_advanced_web_application_firewall
f5	big-ip analytics	cpe:2.3:a:f5:big-ip_analytics
f5	big-ip application acceleration manager	cpe:2.3:a:f5:big-ip_application_acceleration_manager
f5	big-ip application security manager	cpe:2.3:a:f5:big-ip_application_security_manager
f5	big-ip domain name system	cpe:2.3:a:f5:big-ip_domain_name_system
f5	big-ip fraud protection service	cpe:2.3:a:f5:big-ip_fraud_protection_service
f5	big-ip global traffic manager	cpe:2.3:a:f5:big-ip_global_traffic_manager
f5	big-ip link controller	cpe:2.3:a:f5:big-ip_link_controller
f5	big-ip local traffic manager	cpe:2.3:a:f5:big-ip_local_traffic_manager

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
- 16.0.x before 16.0.1.2 and 15.1.x before 15.1.3affected

Affected versions · NVD (20)

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

f5 big-ip access policy manager15.1.0 and later · before 15.1.3
f5 big-ip access policy manager16.0.0 and later · before 16.0.1.2
f5 big-ip advanced firewall manager15.1.0 and later · before 15.1.3
f5 big-ip advanced firewall manager16.0.0 and later · before 16.0.1.2
f5 big-ip advanced web application firewall15.1.0 and later · before 15.1.3
f5 big-ip advanced web application firewall16.0.0 and later · before 16.0.1.2
f5 big-ip analytics15.1.0 and later · before 15.1.3
f5 big-ip analytics16.0.0 and later · before 16.0.1.2
f5 big-ip application acceleration manager15.1.0 and later · before 15.1.3
f5 big-ip application acceleration manager16.0.0 and later · before 16.0.1.2
f5 big-ip application security manager15.1.0 and later · before 15.1.3
f5 big-ip application security manager16.0.0 and later · before 16.0.1.2
f5 big-ip domain name system15.1.0 and later · before 15.1.3
f5 big-ip domain name system16.0.0 and later · before 16.0.1.2
f5 big-ip fraud protection service15.1.0 and later · before 15.1.3
f5 big-ip fraud protection service16.0.0 and later · before 16.0.1.2
f5 big-ip global traffic manager15.1.0 and later · before 15.1.3
f5 big-ip global traffic manager16.0.0 and later · before 16.0.1.2
f5 big-ip link controller15.1.0 and later · before 15.1.3
f5 big-ip link controller16.0.0 and later · before 16.0.1.2

Same product

f5: all records

Other highest-scoring records for the same primary product.

CVE-2022-1388On F5 BIG-IP 16.1.x versions prior to 16.1.2.2, 15.1.x versions prior to 15.1.5.1, 14.1.x versions prior to 14.1.4.6, 13.1.x versions prior…KEV
99Now
CVE-2021-22986On BIG-IP versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, and 12.1.x before 12.1.5.3…KEV
99Now
CVE-2020-5902In BIG-IP versions 15.0.0-15.1.0.3, 14.1.0-14.1.2.5, 13.1.0-13.1.3.3, 12.1.0-12.1.5.1, and 11.6.1-11.6.5.1, the Traffic Management User…KEV
99Now

Published before and after this one in the same product

← EarlierCVE-2021-23022Jun 10, 2021 · On version 7.2.1.x before 7.2.1.3 and 7.1.x before 7.1.9.9 Update 1, the BIG-IP Edge Client Windows Installer Service's temporary folder…
31Monitor
← EarlierCVE-2021-23048Sep 14, 2021 · On BIG-IP version 16.0.x before 16.0.1.2, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, 13.1.x before 13.1.4.1, and all versions of…
30Monitor
Later →CVE-2021-23051Sep 14, 2021 · On BIG-IP versions 15.1.0.4 through 15.1.3, when the Data Plane Development Kit (DPDK)/Elastic Network Adapter (ENA) driver is used with…
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.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

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: high · 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: High

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:H

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 (0)

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

References

support.f5.com/csp/article/K65397301

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

All records