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9.2

NGINX map directive may crash server or run code

CVE-2026-93479 · published 1 day ago
Summary

NGINX Plus, NGINX Open Source and the Debian NGINX package can be forced to overflow memory when a map rule uses regular‑expression captures that are referenced before the map result. An attacker can send specially crafted web requests, causing the server process to restart or, in rare cases, run unwanted code if memory randomization is disabled. Apply the latest NGINX updates or remove such map configurations to eliminate the risk.

What to do
  • Update f5 nginx plus to version 37.1.0.1 or later.
  • Update f5 nginx open source to version 1.31.7 or later.
Affected software
Ecosystem VendorProductAffected versions
– f5 nginx plus < 37.1.0.1
– f5 nginx open source < 1.31.7
Debian:12 debian nginx All versions
Original advisory text
NGINX map directive and regex matching vulnerability
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.
References
Fix within
Internet-facing 3 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically (estimated)
  • Gives an attacker full control (estimated)
Severity
9.2 Critical
Exploitation
<1% chance of attack within 30 days
Type
CWE-122Heap-based Buffer Overflow
Timeline
Published14 Oct 2026
Updated15 Oct 2026
First seen14 Oct 2026
Sources
CVE-2026-93479 · NVD
CVE-2026-93479 · MITRE
DEBIAN-CVE-2026-93479 · OSV
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