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CVE-2026-42533

NGINX Map directive and Regex matching vulnerability

No known exploitation. EPSS puts it in the 59th percentile. Fixed versions are out.

CVSS 3.18.1HighEPSS percentile59th0.9% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix5 products4 fixed builds listed below

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • F5 NGINX PlusAffected: ≥ 37.0.0.1, < 37.0.3.1Upgrade to: 37.0.3.1Affected: ≥ R36, < R36 P7Upgrade to: R36 P7Affected: R33Upgrade to: not statedStated by: CVE record
  • F5 NGINX Open SourceAffected: ≥ 1.31.2, < 1.31.3Upgrade to: 1.31.3Affected: ≥ 0.9.6, < 1.30.4Upgrade to: 1.30.4Stated by: CVE record
  • F5 Nginx Gateway FabricAffected: ≥ 1.3.0, ≤ 1.6.2Upgrade to: after 1.6.2Stated by: NVD
  • F5 Nginx Ingress ControllerAffected: ≥ 3.5.0, ≤ 3.7.2Upgrade to: after 3.7.2Stated by: NVD
  • F5 WafAffected: ≥ 4.11.0, ≤ 4.16.0Upgrade to: after 4.16.0Stated by: NVD

Versions as the sources state them. Full version matrix after sign-in

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

Coverage timeline

2 publishers

  1. F5 releases out-of-band patches for eight vulnerabilities in NGINX and BIG-IP, including a critical heap buffer overflow flaw.

    ·The Hacker News summary

Sourced from public security reporting — each date is when it was published, not when it happened. 1 further article named this CVE in wider roundups without reporting it as a distinct event.

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS59th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.9% chance of exploitation activity in the next 30 days, which ranks it in the 59th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

10 events over 26 days, from the signal feeds we watch.

  1. Patch availablerecord updated
  2. Record updated
  3. OpenVAS check added
  4. Record updated
  5. Publishedweakness classified, att&ck mapped, record updated, record updated

Affected products

And 1 more affected product. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Scored 8.1 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity HighTotal loss of integrity — attacker can modify any data in the component
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

In the news

Watch the software you run.

My Stack ranks new CVEs for your products by real-world exploitation, so the next serious one reaches you without reading every advisory.

We'll flag the next CVE, public exploit or patch for NGINX Plus, not every advisory.