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Full vulnerability report · 2026
CVE-2026-42055High confidence

NGINX ngx_http_proxy_v2_module and ngx_http_grpc_module vulnerability

F5 · NGINX Open Source

Official source article: F5 K000161584 ↗. Check the applicable product and release in the original source.

9.2CriticalCVSS 4.0
Recommended action
Within 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 6.54% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs F5 NGINX Open Source and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Alpine, Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

8 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Alpine v3.23v3.23 · mainnginxVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.1.28.3-r4Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.22v3.22 · mainnginxVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.1.28.3-r4Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.21v3.21 · mainnginxVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.1.26.3-r2Alpine Security Database ↗Source updated 3 Oct 2026
Debian trixietrixie · sourcenginxVendor fix publishedDebian records a fixed source-package version for this release.1.26.3-3+deb13u7Debian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourcenginxVendor fix publishedDebian records a fixed source-package version for this release.1.22.1-9+deb12u9Debian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourcenginxVendor fix publishedDebian records a fixed source-package version for this release.1.30.1-5Debian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourcenginxVendor fix publishedDebian records a fixed source-package version for this release.1.30.1-5Debian Security Tracker ↗Source updated 6 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivenginxVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.1.24.0-2ubuntu7.13Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-42055 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitynginx: NGINX: Arbitrary code execution or Denial of Service via heap-based buffer overflow with crafted HTTP/2 headers
1 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • odf4/odf-console-rhel9 as a component of Red Hat Openshift Data Foundation 4
Summary
A flaw was found in NGINX. When NGINX is configured to proxy HTTP/2 traffic using the ngx_http_proxy_v2_module or ngx_http_grpc_module with specific settings, a remote, unauthenticated attacker can send specially crafted large headers. This can trigger a heap-based buffer overflow, leading to a restart of the NGINX worker process and a Denial of Service (DoS). Under certain conditions, such as when Address Space Layout Randomization (ASLR) is disabled or bypassed, this vulnerability could also allow for arbitrary code execution.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-37718

No EUVD known-exploited evidence

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.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
9.2 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Patch available
01

What, why and how

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.

What

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.

Why

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

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.

Why

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Heap-based Buffer Overflow → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-122 ↗

CWE-122: Heap-based Buffer Overflow. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
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

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCHighVulnerable-system confidentiality: A successful attack can cause a major loss.VIHighVulnerable-system integrity: A successful attack can cause a major loss.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionCWE-122
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-37718Official EUVD mapping

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.

Official EUVD record ↗
BSI · German · WID-SEC-2026-1995NGINX und NGINX Plus: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in NGINX und NGINX NGINX Plus ausnutzen, um Daten zu manipulieren, beliebigen Code auszuführen, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand auszulösen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260624Security Bulletin 24 June 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 24 June 2026, published on 24 June 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0866Multiples vulnérabilités dans Microsoft Azure Linux

u 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53289 du 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53291 du 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53293 du 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53295 du 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53304 du 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53314 du 28 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-52908 du 29 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-52910 du 29 juin 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-42055 du 01 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53329 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53337 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53343 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53347 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53349 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53352 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53353 du 02 juillet 2026 Bulletin de sécurité Microsoft Azure Linux CVE-2026-53355 du 02 juillet 2026 Bulletin de sé

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0775Multiples vulnérabilités dans Nginx

De multiples vulnérabilités ont été découvertes dans Nginx. Elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance, un déni de service à distance et une atteinte à la confidentialité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-022372F5 NetworksのDoS等の複数製品における複数の脆弱性

NGINX Plus および NGINX Open Source には、ngx_http_proxy_v2_module および ngx_http_grpc_module モジュールに脆弱性が存在します。この脆弱性は、HTTP/2 トラフィックをプロキシするために proxy_http_version を 2 に設定する、または grpc_pass ディレクティブを使用し、ignore_invalid_headers ディレクティブが off に設定され、さらに large_client_header_buffers ディレクティブのサイズが 2 メガバイトを超えている場合に発生します。リモートの認証されていない攻撃者は、特定の条件が揃った場合に、アップストリームリクエストを作成する際に大きなヘッダーを送信できる可能性があります。これにより NGINX のワーカープロセスでヒープベースのバッファオーバーフローが発生し、再起動に至る恐れがあります。さらに、ASLR（アドレス空間配置のランダム化）が無効なシステム、あるいは攻撃者が ASLR を回避できる場合には、攻撃者がコードを実行する可能性があります。注: テクニカルサポート終了（EoTS）に達したソフトウェアのバージョンは評価対象外としています。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
odf4/odf-console-rhel9 as a component of Red Hat Openshift Data Foundation 4
Fixed
Action
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 17 Jun 2026 · Last source change 14 Sept 2026, 12:04 UTC · CWE-122 · Heap-based Buffer Overflow

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-37718
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: added remediation: my.f5.com/K000161584.
    Before
    vendor advisory: my.f5.com/K000161584
    After
    remediation: my.f5.com/K000161584 · vendor advisory: my.f5.com/K000161584
    f5sirt@f5.com ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    1.13.10 < 1.31.2; 1.30.2 < 1.30.3; 37.0 < 37.0.2.1; R36 < R36 P6 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    NGINX Open Source: 1.13.10 < 1.31.2, 1.30.2 < 1.30.3; NGINX Plus: 37.0 < 37.0.2.1, R36 < R36 P6 · Fixed: RHSA-2026:36364: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)
    CNA ↗
  3. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    f5sirt@f5.com ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: removed vendor advisory: access.redhat.com/RHSA-2026:58981.
    Before
    vendor advisory: access.redhat.com/RHSA-2026:58981 · vendor advisory: my.f5.com/K000161584
    After
    vendor advisory: my.f5.com/K000161584
    f5sirt@f5.com ↗
  5. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: access.redhat.com/RHSA-2026:58981.
    Before
    vendor advisory: my.f5.com/K000161584
    After
    vendor advisory: access.redhat.com/RHSA-2026:58981 · vendor advisory: my.f5.com/K000161584
    f5sirt@f5.com ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-37718↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference · F5 K000161584↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-42055 · cve.blacktree.nl