CVE-2025-53521

Description

When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Overview

State: PUBLISHED
Assigner (CNA): f5
CVSS severity: CRITICAL
CVSS score: 9.3 / 10
CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Effective score: 9.3 / 10 CRITICAL source: CNA overview
CWE(s): CWE-121
Reserved: 2025-10-03
Published: 2025-10-15 13:55 UTC
Last updated: 2026-03-31 16:04 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2025/53xxx/CVE-2025-53521.json
Linked Threat: CVE-2025-53521 — F5 BIG-IP: F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

CISA Known Exploited Vulnerabilities CISA KEV

CISA has confirmed in-the-wild exploitation of this CVE. Federal agencies must remediate by the due date below; private orgs should treat it as priority-1.

Vulnerability name: F5 BIG-IP Stack-Based Buffer Overflow Vulnerability
Vendor / project: F5
Product: BIG-IP
Date added to KEV: 2026-03-27
Remediation due: 2026-03-30
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Ransomware campaign use: Unknown
CISA notes: Please adhere to F5’s guidelines to assess exposure and mitigate risks. Check for signs of potential compromise on all internet accessible F5 products affected by this vulnerability. For more information please see: https://my.f5.com/manage/s/article/K000156741 ; https://my.f5.com/manage/s/article/K000160486 ; https://my.f5.com/manage/s/article/K11438344 ; https://nvd.nist.gov/vuln/detail/CVE-2025-53521
CISA listing: www.cisa.gov/known-exploited-vulnerabilities-catalog

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2025-10-15 14:15:48 UTC
NVD last modified: 2026-04-02 19:00:01 UTC
NVD CVSS v3.1: 9.8 / 10 CRITICAL source: f5sirt@f5.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitability subscore: 3.9 / 10
Impact subscore: 5.9 / 10
EPSS score: 0.0730 (probability of exploitation in next 30 days)
EPSS percentile: 91.76% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2025-34630
Assigner: f5
Published: Oct 15, 2025, 1:55:52 PM
Updated: Mar 31, 2026, 4:04:27 PM
EUVD base score (CVSS 4.0): 9.3 / 10
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
EUVD-reported EPSS: 8.7700
Vendors: F5
Products: BIG-IP (16.1.0 <16.1.6.1)

BIG-IP (17.5.0 <17.5.1.3)

BIG-IP (15.1.0 <15.1.10.8)

BIG-IP (17.1.0 <17.1.3)
Aliases: GHSA-j3cp-7wh4-9f6c

ENISA description: When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

EUVD references (1)

https://my.f5.com/manage/s/article/K000156741

Affected products (1)

Vendor	Product	Versions	Platforms
F5	BIG-IP	`17.5.0` (affected), `17.1.0` (affected), `16.1.0` (affected), `15.1.0` (affected)	—

Affected products — CPE 2.3 (1) NVD

NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.

cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*

Vendor references (1)

References embedded in the original CVE record by the assigning CNA.

https://my.f5.com/manage/s/article/K000156741 vendor-advisory

Web references (5)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

http://cwe.mitre.org/data/definitions/121.html rapid7:cwe.mitre.org
https://attackerkb.com/topics/CVE-2025-53521 rapid7:attackerkb.com
https://euvd.enisa.europa.eu/vulnerability/EUVD-2025-34630 rapid7:euvd.enisa.europa.eu
https://my.f5.com/manage/s/article/K000156741 rapid7:my.f5.com
https://www.cve.org/CVERecord?id=CVE-2025-53521 rapid7:www.cve.org

NVD-tagged references (2)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://my.f5.com/manage/s/article/K000156741 f5sirt@f5.com Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53521 134c704f-9b21-4f2e-91b3-4a467353bcc0 US Government Resource

Indicators (2)

IOCs linked to the auto-promoted Threat row.

Type	Value	VirusTotal	Attached
cve	`CVE-2025-53521`	no local data	2026-05-14 02:58 UTC
cwe	`CWE-121`	no local data	2026-05-14 02:58 UTC

Remediations (9)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

CVE-2025-53521 | F5 BIG-IP RCE Vulnerability | UpGuard

web:www.upguard.com

CVE-2025-53521 is a critical RCE vulnerability in F5 BIG-IP APM with a 9.8 CVSS score. Actively exploited; immediate patching is required for affected systems.

2026-05-14 11:46 UTC
Microsoft Patch Tuesday May 2026 - 120 Vulnerabilities Fixed, Including ...

web:cybersecuritynews.com

Microsoft's May 2026 Patch Tuesday lands with a heavy enterprise focus, fixing 120 vulnerabilities across Windows, Office, Azure, developer tools, and Microsoft 365 apps, including 29 remote code execution (RCE) flaws rated Critical.

2026-05-14 11:46 UTC
Remediate vulnerabilities with Microsoft Defender Vulnerability ...

web:learn.microsoft.com

Remediate security weaknesses discovered through security recommendations, and create exceptions if needed, in Defender Vulnerability Management.

2026-05-14 11:46 UTC
K000156741: BIG-IP APM vulnerability CVE-2025-53521

web:my.f5.com

( CVE-2025-53521 ) Important: We have learned that this vulnerability has been exploited. If your BIG-IP APM system is running a vulnerable version, or was upgraded from one, please do the following actions: - Review K000160486: Indicators of Compromise for c05d5254.

2026-05-14 11:46 UTC
Security Update Guide - Microsoft

web:portal.msrc.microsoft.com

The Security Update Guide provides information on the latest Microsoft security updates, helping users understand and address potential vulnerabilities effectively.

2026-05-14 11:46 UTC
CISA Warns about Active Exploitation of F5 BIG-IP Vulnerability (CVE ...

web:threatprotect.qualys.com

Tracked as CVE-2025-53521 , successful exploitation of the vulnerability could allow a threat actor to achieve remote code execution. CISA urges users to patch the vulnerability before March 30, 2026. F5 BIG-IP Access Policy Manager (APM) is a flexible, high-performance access management solution from F5 Networks.

2026-05-14 11:46 UTC
CISA Alerts on Actively Exploited F5 BIG-IP Flaw Targeting Organizations

web:cyberpress.org

Flaw, tracked as CVE-2025-53521 , is confirmed to be actively leveraged by threat actors in real-world attacks, placing enterprise and government networks at significant risk.

2026-05-14 11:46 UTC
CVE Record: CVE-2025-53521

web:www.cve.org

Vulnerability detail for CVE-2025-53521 Notice: Expanded keyword searching of CVE Records (with limitations) is now available in the search box above. Learn more here.

2026-05-14 11:46 UTC
CISA Required Action

CISA KEV

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Due date: 2026-03-30 Known ransomware campaign use: Unknown

2026-05-14 01:13 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2025-53521.json.

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