Is CVE-2025-53521 in the CISA KEV catalog?

Yes. CVE-2025-53521 is on the CISA Known Exploited Vulnerabilities list, added 2026-03-27.

What is the CVSS severity of CVE-2025-53521?

CVE-2025-53521 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2025-53521?

CVE-2025-53521 has an EPSS score of 2.21% (81th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-53521?

Upgrade big-ip access policy manager to 17.5.1.3 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2025-53521

CRITICALCISA KEVEPSS 81th pctl

9.8

CVSS v3

NVD

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.

CWE-121Stack-based Buffer Overflow

How to fix

Remediation Available

big-ip access policy managerNVD

Affected:>= 17.5.0, < 17.5.1.3Fixed in:17.5.1.3CVE-2025-53521derived from NVD

big-ip global traffic managerNVD

Affected:>= 17.1.0, < 17.1.3Fixed in:17.1.3CVE-2025-53521derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

2.21%probability of exploitation in 30 days

81stpercentile

Elevated risk: more likely to be exploited than 81% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Remediation due: 2026-03-30

References

Vendor Advisory1

my.f5.com

Government Resource1

cisa.gov

Related Vulnerabilities

Other CWE-121 (Stack-based Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2009-0927	High	8.8	97%	KEV	Fix
CVE-2020-10924	High	8.8	87%	-	-
CVE-2022-20705	Critical	10.0	80%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-03-31.