CVE-2026-42533
NGINX Map directive and Regex matching vulnerability
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'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.
INFO
Published Date :
July 15, 2026, 3:16 p.m.
Last Modified :
July 15, 2026, 4:23 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | 9dacffd4-cb11-413f-8451-fbbfd4ddc0ab | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | CRITICAL | 9dacffd4-cb11-413f-8451-fbbfd4ddc0ab | ||||
| CVSS 4.0 | CRITICAL | [email protected] |
Solution
- Update NGINX Plus and Open Source to a patched version.
- Apply vendor-provided patches and security updates.
- Restart the NGINX worker process after updates.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-42533.
| URL | Resource |
|---|---|
| https://my.f5.com/manage/s/article/K000162097 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-42533 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-42533
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-42533 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-42533 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 15, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-42533', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-07-15T15:37:45.453471Z'} -
New CVE Received by [email protected]
Jul. 15, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'F5', 'modules': ['map directive with regex matching'], 'product': 'NGINX Plus', 'versions': [{'status': 'affected', 'version': '37.0.0.1', 'lessThan': '37.0.3.1', 'versionType': 'custom'}, {'status': 'affected', 'version': 'R36', 'lessThan': 'R36 P7', 'versionType': 'custom'}, {'status': 'affected', 'version': 'R33', 'lessThan': '*', 'versionType': 'custom'}], 'defaultStatus': 'unknown'}, {'vendor': 'F5', 'modules': ['map directive with regex matching'], 'product': 'NGINX Open Source', 'versions': [{'status': 'affected', 'version': '1.31.2', 'lessThan': '1.31.3', 'versionType': 'custom'}, {'status': 'affected', 'version': '0.9.6', 'lessThan': '1.30.4', 'versionType': 'custom'}], 'defaultStatus': 'unknown'}] Added 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'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. Added CVSS V4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-122 Added Reference https://my.f5.com/manage/s/article/K000162097