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CVE Record

CVE-2026-42530: NGINX Open-Source ngx_http_v3_module vulnerability

NGINX Open Source has a vulnerability in the ngx_http_v3_module module. When NGINX Open Source is configured to use the HTTP/3 QUIC module, a remote unauthenticated attacker along with conditions beyond their control can use a specially crafted HTTP/3 session to reopen a QPACK encoder stream. This may cause a Use-after-Free 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. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CriticalCVSS 9.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

NGINX Open Source 1.31.0 can crash when HTTP/3 QUIC support is enabled and a remote unauthenticated attacker triggers a QPACK stream handling flaw. The published rating is critical because code execution is possible if ASLR is disabled or bypassed, but the source notes high attack complexity and conditions outside the attacker’s control.

Executive priority

Treat this as urgent for internet-facing NGINX Open Source 1.31.0 systems using HTTP/3 QUIC. The main business risk is service disruption, with severe compromise possible under weaker memory-protection conditions. Prioritize validation and vendor remediation, but do not assume active exploitation from this bundle alone.

Technical view

The issue is a CWE-416 use-after-free in ngx_http_v3_module. A specially crafted HTTP/3 session can reopen a QPACK encoder stream, causing an NGINX worker process restart. The CVSS 4.0 score is 9.2, with network attack vector, no privileges, no user interaction, and high confidentiality, integrity, and availability impact.

Likely exposure

Exposure appears limited to NGINX Open Source 1.31.0 deployments configured to use the HTTP/3 QUIC module. Systems not serving HTTP/3/QUIC are less likely to be exposed based on the provided description. End-of-Technical-Support versions were not evaluated, so their status is unknown.

Exploitation context

The bundle does not show CISA KEV listing or cited evidence of active exploitation. Exploitation requires a crafted HTTP/3 session plus conditions beyond the attacker’s control. Worker crashes are the clearest expected impact; code execution is described only for systems without ASLR or where ASLR is bypassed.

Researcher notes

Key constraints are high attack complexity, remote unauthenticated reachability, and dependency on HTTP/3 QUIC configuration. The affected list names only NGINX Open Source 1.31.0. Sources do not evaluate EoTS versions, and they do not provide enough detail to assert exploit maturity or broad product impact.

Mitigation direction

  • Check F5 advisory K000161616 for vendor-approved remediation.
  • Review Red Hat RHSA-2026:20351 where Red Hat packages are in use.
  • Disable HTTP/3 QUIC exposure if operationally acceptable until guidance is applied.
  • Confirm ASLR is enabled on affected systems.
  • Prioritize internet-facing NGINX Open Source 1.31.0 instances.

Validation and detection

  • Inventory NGINX Open Source versions and identify 1.31.0 deployments.
  • Confirm whether ngx_http_v3_module and HTTP/3 QUIC are enabled.
  • Review edge configurations for public UDP QUIC exposure.
  • Check vendor advisories for package-specific affected status and fixes.
  • Monitor NGINX worker restarts around HTTP/3 traffic.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-416: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-42530 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.2 (4.0)
Known Exploited
No
Published

Vector: 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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

3CVSS vectors
5Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

3 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.2CVSS 4.0CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——f5
8.1CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9f5
8.1CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

9.2Critical
CVSS 4.0 vector shape for CVE-2026-42530Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: 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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPnginx: ngx_http_v3_module: use-after-free issue leads to denial of service
other:Red Hat severity ratingcvssV3_1
  • 2026-06-17T16:02:06.547Z: Reported to Red Hat.
  • 2026-06-17T14:04:32.173Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
F5NGINX Open Source1.31.0unknown
Weakness

CWE details

CWE-416

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-416 · source CWE mapping

Use After Free

Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs