Threat Intelligence / CVE / CVE-2026-40701

CVE-2026-40701 — F5 NGINX Plus

CVSS v3.1 4.8 (MEDIUM) · CVSS v4.0 6.3 · EPSS 0.0% (higher than 13.9% of all scored CVEs) · Priority 3/10 · Published 2026-05-13

As of 2026-05-13, CVE-2026-40701 is a MEDIUM-severity vulnerability in F5 NGINX Plus, CVSS v3.1 4.8, EPSS 0.0% (13.9th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-40701, most recently “NGINX Rift — CVE-2026-42945 Heap Buffer Overflow in ngx_http_rewrite_module (CVSS v4 9.2 Critical, 18-Year-Old Pre-Auth RCE, Public PoC)”.

Last updated: 2026-05-13

What is CVE-2026-40701?

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssl_module module when the ssl_verify_client directive is set to "on" or "optional," and the ssl_ocsp directive is set to "on" or the leaf parameters are configured with a resolver. With this configuration, an unauthenticated attacker can send requests along with conditions beyond its control that may cause a heap-use-after-free error in the NGINX worker process. This vulnerability may result in limited modification of data or the NGINX worker process restarting. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

The record classifies CVE-2026-40701 under weakness class CWE-416. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction. 2 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 122 days ago.

Severity and exploitation probability

CVSS v3.1 base score
4.8 — MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
CVSS v4.0 base score
6.3
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
EPSS (FIRST)
0.0% probability of exploitation in the next 30 days, higher than 13.9% of all scored CVEs
CISA KEV
Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority
3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published
2026-05-13

Is CVE-2026-40701 being exploited?

It currently carries a trending score of 8 in the Threadlinqs vulnerability feed.

Affected products and versions

How to fix CVE-2026-40701

No vendor patch reference has been recorded for CVE-2026-40701 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-40701

1 tracked threat in the Threadlinqs corpus references CVE-2026-40701, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Seeded from cveorg and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2026-40701 are available via the Threadlinqs MCP server (Purple tier). View plans →

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