NGINX Plus: Use After Free
CVE-2026-97205 is a high-severity use after free vulnerability in NGINX Plus from F5, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 37.1.0.1, 37.0.5.1 as the first without the flaw, so updating NGINX Plus to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.83% chance of exploitation within 30 days, higher than 58% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update NGINX Plus to 37.1.0.1 or 37.0.5.1, whichever matches your release line, or a later version.
- Update NGINX Open Source to 1.31.7 or 1.30.6, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| F5 | NGINX Plus | 37.1.0 up to, but not including, 37.1.0.1; 37.0.0 up to, but not including, 37.0.5.1; R36 and later; R35 and later; R34 and later; R33 and later | 37.1.0.1, 37.0.5.1 |
| F5 | NGINX Open Source | 1.31.0 up to, but not including, 1.31.7; 1.30.0 up to, but not including, 1.30.6 | 1.31.7, 1.30.6 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (f5.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.2 | Critical | CNA (f5.com) |
| CVSS 3.1 | 8.1 | High | CNA (f5.com) |
Official description
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_core_module module. When asynchronous file I/O (AIO) is enabled in certain configurations, processing a Server Side Includes (SSI) page containing “include virtual” commands may trigger a Use-After-Free (UAF) in the NGINX worker process. This may cause memory corruption or a worker process crash. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system, corrupt its memory, or possibly trigger code execution. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in NGINX Plus
- 8.1 High severity
- 8.1 High severity
- 8.2 High severity
- 8.1 High severity
- 8.1 High severity
- 8.1 High severity
Recent Use After Free vulnerabilities
- 7.2 High severity
- 8.1 High severity
- 7.5 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Spotted an error? Tell us.