HighCVE-2026-47774

    Envoy vulnerable to HTTP/2 memory exhaustion via cookie header size bypass and HPACK amplification (CVE-2026-47774)

    Published Last modified Sources: BSI, CVE.org, OSV

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    What is affected, what to do

    Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service.

    An exploit is publicly available. Update Envoy Proxy Envoy to version 1.35.11.

    Affected
    • Envoy Proxy Envoy gte 1.36.0, < 1.36.7..*
    • Envoy Proxy Envoy lt *..1.35.11
    Fixed in
    • Envoy Proxy Envoy 1.35.11

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.5

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: BSI, CVE.org, OSV

    1.0 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 61.8

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    86.86 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    PoC (publicly reported)
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.5 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.5
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    1.0 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    61.8
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 17 June 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-405, CWE-770, CWE-409

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. The issue arises from the combination of two behaviors. First, cookie header bytes are not fully accounted for during request header size validation in Envoy. Second, HPACK header block limits in oghttp2/quiche are enforced on encoded bytes without a corresponding limit on total decoded header size. Together, these behaviors allow a malicious client to cause large decoded header allocations while bypassing the intended request header size protections. Versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a fix. No complete workaround is known short of applying a fix. Possible temporary mitigations include disabling downstream HTTP/2 where operationally feasible; enforcing stricter request header and cookie limits before traffic reaches Envoy; and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic.

    Source: BSI WID Portal, BSI CSAF, NVD (NIST), CVE.org (MITRE), OSV (Open Source Vulnerabilities), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    envoyproxyenvoy
    • ≥ 1.36.0, < 1.36.7
    • < 1.35.11
    • 1.36.0 – < 1.36.7
    • < 1.35.11
    • 1.38.0
    • 1.37.0 – < 1.37.3
    • —
    • 1.35.11
    • 1.36.7
    • 1.35.11
    • —
    • 1.37.3
    redhatopenshift_service_mesh
    • 3.0 – < 3.0.12
    • 3.2 – < 3.2.6
    • 2.6 – < 2.6.17
    • 3.3 – < 3.3.4
    • 3.1 – < 3.1.9
    • 3.0.12
    • 3.2.6
    • 2.6.17
    • 3.3.4
    • 3.1.9
    Red HatOpenShift
    • Mesh 3.0.12
    • Mesh 3.2.6
    • Mesh 3.3.4
    • Mesh 3.1.9
    • —
    • —
    • —
    • —
    Distribution and container packages (3)

    Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

    Distribution and container packages
    Affected versionsFixed in
    bitnamienvoy
    • 1.37.0
    • 1.36.0
    • 1.38.0
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-405Asymmetric Resource Consumption (Amplification)

      Class

      The product does not properly control situations in which an adversary can cause the product to consume or produce excessive resources without requiring the adversary to invest equivalent work or otherwise prove authorization, i.e., the adversary's influence is "asymmetric."

      Entry at MITRE CWE-405

    • CWE-770Allocation of Resources Without Limits or Throttling

      Base

      The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

      Entry at MITRE CWE-770

    • CWE-409Improper Handling of Highly Compressed Data (Data Amplification)

      Base

      The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.

      Entry at MITRE CWE-409

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    Reference tagged as exploitbugzilla.redhat.com (opens in a new tab)PoC (publicly reported)reported, not verified—

    References & sources

    • openwall.comlists/oss-security/2026/06/04/15web, Mailing list, Mitigation, Third-party advisory
    • github.comenvoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8web, x_refsource_CONFIRM, Mitigation, Vendor advisory
    • NVD (NIST)vuln/detail/CVE-2026-47774web
    • access.redhat.comerrata/RHSA-2026:26210web, Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • access.redhat.comerrata/RHSA-2026:26222web, Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • access.redhat.comerrata/RHSA-2026:26231web, Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • access.redhat.comerrata/RHSA-2026:26247web, Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • access.redhat.comerrata/RHSA-2026:27114web, Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • access.redhat.comsecurity/cve/CVE-2026-47774web, Vulnerability database, x_refsource_REDHAT, Third-party advisory
    • bugzilla.redhat.comRHBZ#2487465web, Issue tracking, x_refsource_REDHAT, Exploit, Issue tracking, Third-party advisory
    • security.access.redhat.comdata/csaf/v2/vex/2026/cve-2026-47774.jsonweb, x_sadp-csaf-vex, Third-party advisory

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      Red Hat OpenShift Service Mesh 2.6, Red Hat OpenShift Service Mesh 3, Red Hat OpenShift Service Mesh 3.1 (+2)
      Red Hat OpenShift Service Mesh 2.6, Red Hat OpenShift Service Mesh 3.0, Red Hat OpenShift Service Mesh 3.1 (+2)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    2. Initial analysis by NVDNVD

      Newly listed as affected:
      Show 12 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions up to (excluding) 1.35.11 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.36.0 up to (excluding) 1.36.7 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.37.0 up to (excluding) 1.37.3 *cpe:2.3:a:envoyproxy:envoy:1.38.0:*:*:*:*:*:*:*
      Product configurationadded
      —
      OR *cpe:2.3:a:redhat:openshift_service_mesh:*:*:*:*:*:*:*:* versions from (including) 2.6 up to (excluding) 2.6.17 *cpe:2.3:a:redhat:openshift_service_mesh:*:*:*:*:*:*:*:* versions from (including) 3.0 up to (excluding) 3.0.12 *cpe:2.3:a:redhat:openshift_service_mesh:*:*:*:*:*:*:*:* versions from (including) 3.1 up to (excluding) 3.1.9 *cpe:2.3:a:redhat:openshift_service_mesh:*:*:*:*:*:*:*:* versions from (including) 3.2 up to (excluding) 3.2.6 *cpe:2.3:a:redhat:openshift_service_mesh:*:*:*:*:*:*:*:* versions from (including) 3.3 up to (excluding) 3.3.4
      Reference typeadded
      —
      GitHub, Inc.: https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8 Types: Mitigation, Vendor Advisory
      Reference typeadded
      —
      CVE: http://www.openwall.com/lists/oss-security/2026/06/04/15 Types: Mailing List, Mitigation, Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://access.redhat.com/errata/RHSA-2026:26210 Types: Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://access.redhat.com/errata/RHSA-2026:26222 Types: Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://access.redhat.com/errata/RHSA-2026:26231 Types: Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://access.redhat.com/errata/RHSA-2026:26247 Types: Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://access.redhat.com/errata/RHSA-2026:27114 Types: Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://access.redhat.com/security/cve/CVE-2026-47774 Types: Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://bugzilla.redhat.com/show_bug.cgi?id=2487465 Types: Exploit, Issue Tracking, Third Party Advisory
      Reference typeadded
      —
      redhat-SADP: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.json Types: Third Party Advisory

      Source identifier: nvd@nist.gov

    3. ReceivedGitHub

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

      Weakness type: CWE-405, CWE-770

      Description added or changed

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      envoy
      Descriptionadded
      —
      Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. The issue arises from the combination of two behaviors. First, cookie header bytes are not fully accounted for during request header size validation in Envoy. Second, HPACK header block limits in oghttp2/quiche are enforced on encoded bytes without a corresponding limit on total decoded header size. Together, these behaviors allow a malicious client to cause large decoded header allocations while bypassing the intended request header size protections. Versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a fix. No complete workaround is known short of applying a fix. Possible temporary mitigations include disabling downstream HTTP/2 where operationally feasible; enforcing stricter request header and cookie limits before traffic reaches Envoy; and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic.
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
      Weakness type (CWE)added
      —
      CWE-405
      Weakness type (CWE)added
      —
      CWE-770
      Referenceadded
      —
      https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8

      Source identifier: security-advisories@github.com

    4. Record modifiedCVE Program

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2026/06/04/15

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    One NVD translation into another language is hidden.

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