F5 NGINX fixes a critical vulnerability

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[TLP:CLEAR] F5 NGINX fixes a critical vulnerability

F5 Networks fixes a critical vulnerability in NGINX [1]. Fixed versions of the individual products: NGINX Plus - 37.0.3.1, R36 P7 NGINX Open Source - 1.31.3, 1.30.4 F5 WAF for NGINX - 5.13.4 NGINX Gateway Fabric - 2.6.7 NGINX Ingress Controller - 5.5.3, 2026-lts-r4

F5 NGINX - DoS, RCE (CVE-2026-42533)

CVSS 9.2 (Critical)

An unauthenticated remote attacker can, under certain conditions, perform a DoS attack on NGINX and potentially also execute code by sending specially crafted HTTP requests. The vulnerability can be exploited on specifically configured systems that use the map directive with regular expressions in combination with a non-standard order of variable referencing. If an immediate update to the fixed version is not possible, the risk can be temporarily mitigated by replacing unnamed variables with named ones and restricting their referencing exclusively to the configuration block in which they were defined [1].

The vulnerability is present in products:

NGINX Plus; >=37.0.0.1, <37.0.3.1; >=R33, <R36 P7;
NGINX Open Source; >=1.30.0, <1.30.4; ==1.31.2;
NGINX Instance Manager; >=5.9.0, <5.13.4;
NGINX App Protect WAF; >=4.11.0, <=4.16.0; >=5.2.0, <=5.8.0;
NGINX Gateway Fabric; >=1.3.0, <=1.6.2; >=2.0.0, <2.6.7;
NGINX Ingress Controller; >=3.5.0, <=3.7.2; >=4.0.0, <=4.0.1; >=5.0.0, <5.5.3; >=2026-lts-r1, <2026-lts-r4;

CVSS: 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

More information:

CVE-2026-42533 at cve.org, NVD
CWE-122: Heap-based Buffer Overflow at cwe.mitre.org

The vulnerability was publicly disclosed 15. 7. 2026.

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[TLP:CLEAR] F5 NGINX fixes a critical vulnerability

F5 NGINX - DoS, RCE (CVE-2026-42533)

CVSS 9.2 (Critical)

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