Vulnary
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Critical· 9.2

CVE-2026-9256

NGINX Plus and NGINX Open Source have a critical flaw in the rewrite module that can be triggered by specially crafted URLs. The bug can cause a heap buffer overflow in the worker process, leading to a restart and, on systems without ASLR, potential code execution.

publishedMay 22, 2026
last modifiedJul 24, 2026
sourcesNVD
severity · cvss
9.2
critical · how bad it is
exploitation · epss
10%
95th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Sep 6, 2026

No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.

01

Who is affected

NGINX Plus and NGINX Open Source, including version 1.31.0 and other releases that have not yet reached End of Technical Support.

02

Real-world impact

An attacker can send a crafted HTTP request that triggers a heap buffer overflow, causing the NGINX worker to crash. On systems with ASLR disabled or bypassed, the attacker may also execute arbitrary code.

03

Why this severity

The CVSS score of 9.2 reflects the high impact of the vulnerability: it can lead to denial of service and, under certain conditions, remote code execution. The attack requires no authentication and is performed over the network, but the complexity is high due to the need for a specific regex pattern.

04

What to do about it

no official fix yet

No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.

No fix documented in sources

05

Timeline

  1. May 22, 2026 · May 22, 2026
    Published
    Disclosed and added to the National Vulnerability Database.
  2. Jul 24, 2026 · 11d ago
    Advisory updated
    The NVD record was last revised.
06

How it’s attacked

Attack vectorNetwork (remote)
Attack complexityHigh
Attack requirementsPresent
Privileges requiredNone
User interactionNone needed
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
07

References & advisories

NVD advisory ↗Search advisories ↗
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →