How severe is CVE-2026-8711?

CVE-2026-8711 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-8711 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-8711?

CVE-2026-8711 affects F5 Njs. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-8711?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-8711 have an EU (EUVD) identifier?

Yes. CVE-2026-8711 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30940.

When was CVE-2026-8711 published?

CVE-2026-8711 was published on 2026-05-19 and last updated on 2026-06-17.

CVE-2026-8711

CVE-2026-8711 is a high-severity vulnerability in F5 Njs with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-122.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v4: 9.2
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30940
Weakness: CWE-122
Affected product: F5 Njs
Published: 2026-05-19
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-8711?: 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.
How severe is CVE-2026-8711?: CVE-2026-8711 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-8711 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-8711?: CVE-2026-8711 affects F5 Njs. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-8711?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-8711 have an EU (EUVD) identifier?: Yes. CVE-2026-8711 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30940.
When was CVE-2026-8711 published?: CVE-2026-8711 was published on 2026-05-19 and last updated on 2026-06-17.

References

https://my.f5.com/manage/s/article/K000161307

Affected products (1)

cpe:2.3:a:f5:njs:*:*:*:*:*:*:*:*

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