Exploitation evidence
Known exploited · CISA KEV listed
Added 2026-03-27. Ransomware campaign use: Unknown.
CISA 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.
CISA due date: 2026-03-30. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
F5 / BIG-IP
Default status: unknown
- affected: 17.5.0 to < 17.5.1.3 (custom)
- affected: 17.1.0 to < 17.1.3 (custom)
- affected: 16.1.0 to < 16.1.6.1 (custom)
- affected: 15.1.0 to < 15.1.10.8 (custom)
Fixes and workarounds
No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.
Sources and related reporting
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.02295,
"percentile": 0.83513
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.02295,
"percentile": 0.83408
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.02295,
"percentile": 0.83388
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.02295,
"percentile": 0.83376
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.02295,
"percentile": 0.83365
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.02295,
"percentile": 0.83339
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.02295,
"percentile": 0.83326
}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.02295,
"percentile": 0.83311
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.02295,
"percentile": 0.8328
}03 Nov 2026, 18:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2025-53521",
"options": [
{
"Exploitation": "active"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-28T03:55:47.100165Z",
"version": "2.0.3"
},
"type": "ssvc"
}
},
{
"other": {
"content": {
"dateAdded": "2026-03-27",
"reference": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53521"
},
"type": "kev"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-03-29T13:56:45.917Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"government-resource"
],
"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53521"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unknown",
"modules": [
"APM"
],
"product": "BIG-IP",
"vendor": "F5",
"versions": [
{
"lessThan": "17.5.1.3",
"status": "affected",
"version": "17.5.0",
"versionType": "custom"
},
{
"lessThan": "17.1.3",
"status": "affected",
"version": "17.1.0",
"versionType": "custom"
},
{
"lessThan": "16.1.6.1",
"status": "affected",
"version": "16.1.0",
"versionType": "custom"
},
{
"lessThan": "15.1.10.8",
"status": "affected",
"version": "15.1.0",
"versionType": "custom"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "F5 would like to thank Kristian Vlaardingerbroek, Hugo Trippaers, and other people of Schuberg Philis; Bart Vrancken; Fox-IT; and the National Cyber Security Centre (NCSC) in the Netherlands for their assistance in investigating this issue and following the highest standards of coordinated disclosure."
}
],
"datePublic": "2025-10-15T14:00:00.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "<span style=\"background-color: rgb(255, 255, 255);\"><span style=\"background-color: rgb(255, 255, 255);\">When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE).</span> \n\nNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated.\n\n</span>"
}
],
"value": "When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). \n\nNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
},
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 9.3,
"baseSeverity": "CRITICAL",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-121",
"description": "CWE-121 Stack-based Buffer Overflow",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-03-31T16:04:27.360Z",
"orgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
"shortName": "f5"
},
"references": [
{
"tags": [
"vendor-advisory"
],
"url": "https://my.f5.com/manage/s/article/K000156741"
}
],
"source": {
"discovery": "INTERNAL"
},
"title": "BigIP APM Vulnerability",
"x_generator": {
"engine": "F5 SIRTBot v1.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
"assignerShortName": "f5",
"cveId": "CVE-2025-53521",
"datePublished": "2025-10-15T13:55:52.694Z",
"dateReserved": "2025-10-03T23:04:38.083Z",
"dateUpdated": "2026-03-31T16:04:27.360Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.02295,
"percentile": 0.8326
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2025-53521",
"cwes": [
"CWE-121"
],
"dateAdded": "2026-03-27",
"dueDate": "2026-03-30",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"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",
"product": "BIG-IP",
"requiredAction": "Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.",
"shortDescription": "F5 BIG-IP APM contains a stack-based buffer overflow vulnerability that could allow a threat actor to achieve remote code execution.",
"vendorProject": "F5",
"vulnerabilityName": "F5 BIG-IP Stack-Based Buffer Overflow Vulnerability"
}