F5 NGINX Plus/NGINX Open Source Configuration ngx_http_ssl_module use after free

CVSS Meta Temp Score
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CTI Interest Score
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5.9$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in F5 NGINX Plus and NGINX Open Source. Affected by this vulnerability is the function ngx_http_ssl_module of the component Configuration Handler. Performing a manipulation results in use after free. This vulnerability is identified as CVE-2026-40701. The attack can be initiated remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in F5 NGINX Plus and NGINX Open Source (affected version not known). It has been classified as critical. This affects the function ngx_http_ssl_module of the component Configuration Handler. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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 weakness was released by Zhenpeng as K000161021. The advisory is shared at my.f5.com. This vulnerability is uniquely identified as CVE-2026-40701 since 05/01/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/30/2026).

The vulnerability scanner Nessus provides a plugin with the ID 314992 (Fedora 42 : nginx / nginx-mod-brotli / nginx-mod-fancyindex / etc (2026-38623b4fed)), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (314992) and CERT Bund (WID-SEC-2026-1527). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Fedora Linux
  • Ubuntu Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • NGINX NGINX Plus
  • NGINX NGINX
  • SUSE Linux

Productinfo

Type

Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 6.1
VulDB Meta Temp Score: 5.9

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.8
CNA Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 314992
Nessus Name: Fedora 42 : nginx / nginx-mod-brotli / nginx-mod-fancyindex / etc (2026-38623b4fed)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Timelineinfo

05/01/2026 CVE reserved
05/13/2026 +12 days Advisory disclosed
05/13/2026 +0 days VulDB entry created
06/30/2026 +48 days VulDB entry last update

Sourcesinfo

Vendor: f5.com

Advisory: K000161021
Researcher: Zhenpeng
Status: Confirmed

CVE: CVE-2026-40701 (🔒)
GCVE (CVE): GCVE-0-2026-40701
GCVE (VulDB): GCVE-100-363561
CERT Bund: WID-SEC-2026-1527 - NGINX Open Source and NGINX Plus: Mehrere Schwachstellen

Entryinfo

Created: 05/13/2026 17:43
Updated: 06/30/2026 16:02
Changes: 05/13/2026 17:43 (77), 05/15/2026 21:18 (7), 05/16/2026 10:02 (2), 06/30/2026 16:02 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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