F5 NGINX Open Source/NGINX Plus Response Header ngx_mail_auth_http_module null pointer dereference

CVSS Meta Temp Score
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CTI Interest Score
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7.3$0-$5k0.16

Summaryinfo

A vulnerability identified as problematic has been detected in F5 NGINX Open Source and NGINX Plus. Affected by this vulnerability is the function ngx_mail_auth_http_module of the component Response Header Handler. The manipulation leads to null pointer dereference. This vulnerability is documented as CVE-2026-27651. 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 Open Source and NGINX Plus (affected version not known). It has been rated as critical. This issue affects the function ngx_mail_auth_http_module of the component Response Header Handler. The manipulation with an unknown input leads to a null pointer dereference vulnerability. Using CWE to declare the problem leads to CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. Impacted is availability. The summary by CVE is:

When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

The advisory is shared at my.f5.com. The identification of this vulnerability is CVE-2026-27651 since 03/18/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 303484 (Linux Distros Unpatched Vulnerability : CVE-2026-27651), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (303484). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

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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: 7.5
VulDB Meta Temp Score: 7.3

VulDB Base Score: 7.5
VulDB Temp Score: 7.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.5
CNA Vector: 🔒

CVSSv2info

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

Exploitinginfo

Class: Null pointer dereference
CWE: CWE-476 / CWE-404
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: 303484
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-27651

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Timelineinfo

03/18/2026 CVE reserved
03/24/2026 +6 days Advisory disclosed
03/24/2026 +0 days VulDB entry created
03/29/2026 +5 days VulDB entry last update

Sourcesinfo

Vendor: f5.com

Advisory: K000160383
Status: Confirmed

CVE: CVE-2026-27651 (🔒)
GCVE (CVE): GCVE-0-2026-27651
GCVE (VulDB): GCVE-100-352781

Entryinfo

Created: 03/24/2026 16:07
Updated: 03/29/2026 03:05
Changes: 03/24/2026 16:07 (76), 03/25/2026 08:22 (2), 03/29/2026 03:05 (1)
Complete: 🔍
Cache ID: 216:54D:103

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