CVE-2026-94127
CVE-2026-94127 is a security flaw in F5 BIG-IP APM, equipment big companies use to route traffic to their websites and apps. Attackers can run their own code on F5 BIG-IP APM from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 22 Sep 2026.[1]
F5 BIG-IP APM is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version Hotfix-BIGIP-21.1.0.2.0.30.22-ENG, Hotfix-BIGIP-17.5.1.9.0.160.12-ENG and Hotfix-BIGIP-17.1.3.5.0.41.14-ENG of BIG-IP.
Description
CISA calls it a heap-based buffer overflow in F5 BIG-IP APM. In its words: “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.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is heap buffer overflow (CWE-122), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| BIG-IP | Hotfix-BIGIP-21.1.0.2.0.30.22-ENG |
| BIG-IP | Hotfix-BIGIP-17.5.1.9.0.160.12-ENG |
| BIG-IP | Hotfix-BIGIP-17.1.3.5.0.41.14-ENG |
Most families won’t have F5 BIG-IP APM; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 22 Sep 2026, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 25 Sep 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 27%. That’s in the top 2% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
F5 has published a fix or advice.[3] CISA’s 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).”[1]
- Check whether you use it.F5 BIG-IP APM is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version Hotfix-BIGIP-21.1.0.2.0.30.22-ENG, Hotfix-BIGIP-17.5.1.9.0.160.12-ENG and Hotfix-BIGIP-17.1.3.5.0.41.14-ENG of BIG-IP), or not in use. CISA gave US government agencies until 25 Sep 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 27%.[4] |
See also
Other F5 flaws
- CVE-2025-53521, F5 BIG-IP: stack-based buffer overflow ·
- CVE-2023-46748, F5 BIG-IP Configuration Utility: SQL injection ·
- CVE-2023-46747, F5 BIG-IP Configuration Utility: authentication bypass ·
- CVE-2022-1388, F5 BIG-IP: missing authentication ·
- CVE-2021-22991, F5 BIG-IP Traffic Management Microkernel: buffer overflow ·
Other heap buffer overflow flaws
- CVE-2025-25249, Fortinet products: heap-based buffer overflow ·
- CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
- CVE-2025-32706, Microsoft Windows: common log file system (CLFS) driver heap-based buffer overflow ·
- CVE-2025-24993, Microsoft Windows: NTFS heap-based buffer overflow ·
- CVE-2025-21418, Microsoft Windows: ancillary function driver for winSock heap-based buffer overflow ·
Added the same day
- CVE-2026-93952, Arista VeloCloud Orchestrator: improper input validation ·
- CVE-2026-93616, Check Point products: path traversal ·
- CVE-2026-85102, Check Point products: improper certificate validation ·
Every F5 flaw on CISA’s list · Everything added in September 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “F5 BIG-IP APM Heap-based Buffer Overflow Vulnerability”. Known Exploited Vulnerabilities Catalog, added 22 Sep 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-94127 Detail”. National Vulnerability Database, published 22 Sep 2026.
- ^ F5. Advisories and fixes: my.f5.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.266, percentile 98.0, 31 Oct 2026.
- CVE Program. “CVE-2026-94127”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.