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CVE-2025-53521VulnerabilityPublished Updated

CVE-2025-53521: F5 BIG-IP · Stack-based Buffer Overflow

Affects F5 BIG-IPSource CVE Database V5

0

Exploited in the wild · KEV due 30 Mar 2026 · 2% EPSS : apply the vendor's fix or mitigations to F5 BIG-IP now.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
KEV deadline
 US federal agencies must patch by this date; a sensible deadline for everyone else.
EPSS
2.2% chance of exploitation in 30 days – higher than 83% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 15 Oct 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: evidence found.

    Listed in CISA KEV 163 days after disclosure

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by F5, Inc.

    , 12 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. In Threat Radar

    record ingested

    , 7 minutes after disclosure

  4. , 163 days after disclosure

  5. KEV remediation due

    US federal deadline

    , 166 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Affected software

ProductAffectedFixed in
F5f5/big-ippkg:rpm/f5/big-ipOther threatsAffected
  • =15.1.0
  • =16.1.0
  • =17.1.0
  • =17.5.0
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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.

References

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