CVE-2026-8711: F5 NGINX JavaScript · Heap-based Buffer Overflow
Affects F5 NGINX JavaScriptSource CVE Database V5
Not known to be exploited · CVSS 8.1 High : upgrade to 0.9.9 soon.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 9.6% chance of exploitation in 30 days – higher than 95% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 0.9.9
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 19 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade F5 NGINX JavaScript to 0.9.9.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| F5NGINX JavaScript | Affected
| Fixed in
|
AI-suggested
If you cannot patch yet, avoid configuring js_fetch_proxy with client-controlled variables or disable the affected functionality if possible.
Description
NGINX JavaScript has a vulnerability when the js_fetch_proxy directive is configured with at least one client-controlled NGINX variable (for example, $http_*, $arg_*, $cookie_*) and a location invoking the ngx.fetch() operation from NGINX JavaScript. An unauthenticated attacker can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.