Security Digest · Vulnerability record · Known exploited
CVE-2026-94127: F5 BIG-IP APM Heap-based Buffer Overflow Vulnerability
Exploited in the wild (CISA KEV). When a BIG-IP APM access policy and an OAuth profile are configured on a virtual server, specific malicious traffic can lead to remote code execution (RCE).
CISA KEV · added 2026-09-22 CVSS 9.3 Critical EPSS 2.2% · p83 Patch this week
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run F5 BIG-IP APM. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-09-22, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-09-25; treat that as the outer limit, not the target.
- EPSS 2.2%, percentile 83: FIRST’s model estimates a 2.2% chance of exploitation activity in the next 30 days, higher than 83% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Patch this week. F5 Breach: Nation-State Stole BIG-IP Source Code — The breach itself needs no new action a year on, but its aftermath does: two unauthenticated BIG-IP APM RCEs are now on CISA's exploited list, so every BIG-IP owner should be on current fixed builds with management interfaces off the internet.
What it is
When a BIG-IP APM access policy and an OAuth profile are configured on a virtual server, specific malicious traffic can lead to remote code execution (RCE). This vulnerability is only present when BIG-IP APM is configured as an OAuth Authorization Server. Deployments using APM strictly as an OAuth Client / Resource Server (without OAuth authorization server profiles configured) are not affected by this vulnerability. Impact: This vulnerability allows an unauthenticated attacker to perform remote code execution. The BIG-IP system in Appliance mode is also vulnerable. This is a data plane issue; there is no control plane exposure. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
CISA’s summary
F5 BIG-IP APM contains a heap-based buffer overflow vulnerability when access policy and an OAuth profile are configured on a virtual server. This vulnerability could allow an unauthenticated attacker to perform remote code execution.
Weakness type: CWE-122.
Product: F5 BIG-IP APM · Assigned by: f5 · Published: 2026-09-22
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| F5 | BIG-IP | 21.1.0 < Hotfix-BIGIP-21.1.0.2.0.30.22-ENG, 17.5.0 < Hotfix-BIGIP-17.5.1.9.0.160.12-ENG, 17.1.0 < Hotfix-BIGIP-17.1.3.5.0.41.14-ENG |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| f5 | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| f5 | 4.0 | 9.3 Critical | 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 |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Attack requirements: none
- Privileges required: none (no login)
- User interaction: none
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2026-09-22; federal due date 2026-09-25. Known ransomware use: Unknown.
- CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 2.23% probability of exploitation activity in the next 30 days; percentile 83.
Timeline
- — erroneo.us brief: F5 Breach: Nation-State Stole BIG-IP Source Code
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CVE record published by f5
- — CVE record last updated
- — CISA remediation deadline for US federal agencies
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- my.f5.com my.f5.com
Vulnerability records
- CVE.org record CVE-2026-94127 cve.org
- NVD entry CVE-2026-94127 nvd.nist.gov