Heap buffer overflow
A write runs past allocated heap storage and can damage neighbouring data.
CWE-122 · CISA KEV; NVD record: f5sirt@f5.com
Video course · Free course. C programming and memory concepts are useful; covers several weakness types.
Exploited. On CISA's list since 2026-09-22.
F5 BIG-IP APM Heap-based Buffer Overflow Vulnerability
CVE-2026-94127 · F5 BIG-IP APM · Published 2026-09-22
How bad would it be?
9.3 out of 10
CVSS rates it critical: about as damaging as flaws get.
How likely is it to be used?
25%
Estimated chance of exploitation in the next 30 days, higher than 97% of all scored flaws (EPSS, 2026-10-29).
Is it already being used?
Yes
CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 35 days ago (2026-09-25).
What CISA says to do
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.
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.
What the flaw 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.
From the NVD.
Fixes and advisories
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Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.