CVE-2026-93479

NGINX map directive and regex matching vulnerability

Published Oct 14, 2026 CVSS 4.0 · 9.2 Critical EPSS 1.2% KEV · Not listed
Description
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control 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.

Impact: 
This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Remediation

Vendor Workaround

To mitigate this vulnerability, do not use unnamed captures. Use named captures instead and limit their usage to the block with the regex match.

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-6575-1 nginx security update
Ubuntu USN Ubuntu USN USN-8955-1 nginx vulnerabilities
History
Type Values Removed Values Added
First Time appeared F5
F5 nginx Open Source
F5 nginx Plus
Vendors & Products F5
F5 nginx Open Source
F5 nginx Plus
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control 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. Impact:  This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Title NGINX map directive and regex matching vulnerability
Weaknesses CWE-122
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 9.2, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
f5
Published
Updated
Oct 29, 2026, 4:59 PM
Reserved
Sep 30, 2026, 9:56 PM
Status
Awaiting Analysis
Published
Oct 14, 2026, 3:17 PM
Modified
Oct 15, 2026, 11:18 AM
Severity
Important
Public date
Oct 14, 2026, 2:40 PM