CVE-2026-42533
Severity CVSS v4.0:
CRITICAL
Type:
CWE-122
Heap-based Buffer Overflow
Publication date:
15/07/2026
Last modified:
16/07/2026
Description
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map&#39;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.<br />
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Impact:<br />
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.<br />
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Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Impact
Base Score 4.0
9.20
Severity 4.0
CRITICAL
Base Score 3.x
8.10
Severity 3.x
HIGH