CVE-2025-53521: F5 BIG-IP · Stack-based Buffer Overflow
Affects F5 BIG-IPSource CVE Database V5
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
- 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:HExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 15 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 163 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by F5, Inc.
, 12 days before disclosure
CVE published
on cve.org
, t = 0
In Threat Radar
record ingested
, 7 minutes after disclosure
Added to CISA KEV (opens in a new tab)
exploitation confirmed
, 163 days after disclosure
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
| Product | Affected | Fixed in |
|---|---|---|
F5f5/big-ippkg:rpm/f5/big-ipOther threats | Affected
| 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.