LiveActive security incident?Get immediate response
CVE Record

CVE-2026-42055: NGINX ngx_http_proxy_v2_module and ngx_http_grpc_module vulnerability

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request. This may cause a heap-based 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. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CriticalCVSS 9.2Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

This is a critical NGINX issue, but exposure depends on an uncommon configuration combination. A remote unauthenticated attacker may be able to crash worker processes, causing restart. Code execution is only stated for systems without ASLR or where ASLR can be bypassed.

Executive priority

Treat as urgent for externally exposed NGINX reverse proxies using HTTP/2 or gRPC. The likely footprint is configuration-specific, but the worst-case impact justifies rapid inventory, vendor patch review, and prioritized remediation.

Technical view

The vulnerability affects ngx_http_proxy_v2_module and ngx_http_grpc_module when proxying HTTP/2 traffic with proxy_http_version 2 or grpc_pass, ignore_invalid_headers off, and large_client_header_buffers over 2MB. Large headers during upstream request creation can trigger a heap-based buffer overflow in the worker process.

Likely exposure

Internet-facing NGINX deployments are most relevant when they proxy HTTP/2 or gRPC traffic and meet all listed directive conditions. End-of-Technical-Support versions were not evaluated, so legacy deployments need separate vendor review.

Exploitation context

The source bundle does not show CISA KEV listing or cited active exploitation. Attack requires network access, no authentication, high complexity, and a prerequisite configuration state. Impact ranges from worker restart to code execution where ASLR is disabled or bypassed.

Researcher notes

Evidence supports a heap-based buffer overflow with CWE-122 and CWE-131. The CVSS v4 score is 9.2 with high confidentiality, integrity, and availability impact, but attack complexity is high and active exploitation is not supported by the provided sources.

Mitigation direction

  • Review F5 and Red Hat advisories for supported fixed packages or guidance.
  • Apply applicable vendor errata where your distribution or product is covered.
  • Identify NGINX configurations meeting all documented preconditions.
  • Prioritize internet-facing HTTP/2 and gRPC proxy services for remediation.
  • Avoid unsupported or End-of-Technical-Support NGINX versions where possible.

Validation and detection

  • Inventory NGINX Open Source and NGINX Plus versions in production.
  • Search configurations for proxy_http_version 2, grpc_pass, ignore_invalid_headers off, and large_client_header_buffers over 2MB.
  • Confirm whether affected services accept untrusted external traffic.
  • Check Red Hat advisories for package status on managed platforms.
  • Document systems where ASLR is disabled or cannot be verified.
Prepared
Confidence
high
Sources
12

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-122: 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.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-131: 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.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-42055 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.2 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:H/AT:P/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
11Source 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:P/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-2026-42055Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:H/AT:P/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: NGINX: Arbitrary code execution or Denial of Service via heap-based buffer overflow with crafted HTTP/2 headers
other:Red Hat severity ratingcvssV3_1
  • 2026-06-17T16:01:41.848Z: Reported to Red Hat.
  • 2026-06-17T14:04:32.520Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
F5NGINX Open Source1.13.10, 1.30.2unknown
F5NGINX Plus37.0, R36unaffected
Weakness

CWE details

CWE-122CWE-131

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

CWE-122 · source CWE mapping

Heap-based Buffer Overflow

Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-131 · source CWE mapping

Incorrect Calculation of Buffer Size

Incorrect Calculation of Buffer Size represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs