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Full vulnerability report · 2026
CVE-2026-48044High confidence

Envoy Zstd Decompressor: Ratio Check at Wrong Loop Depth lead to memory explosion

envoyproxy · envoy

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
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-2026-48044 · CSAF 2.0 · revision 3 · finalRed Hat Product SecurityEnvoy: Envoy: Denial of Service via specially crafted zstd payload
1 known affected

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

  • openshift-service-mesh/proxyv2-rhel9 as a component of OpenShift Service Mesh 2
Summary
A flaw was found in Envoy, an open source edge and service proxy. A remote attacker can exploit this vulnerability by sending a specially crafted, highly compressed zstd payload to an Envoy proxy with zstd decompression enabled. This can lead to massive memory allocation, causing severe memory exhaustion and potentially resulting in an Out-Of-Memory (OOM) kill and Denial of Service (DoS) for the Envoy proxy.
Remediation
See Red Hat OpenShift Service Mesh 3.0.14 documentation at https://docs.redhat.com/en/documentation/red_hat_openshift_service_mesh/3.0
Optional official sources

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

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

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-2026-39820

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

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
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.23.0 until 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability has been identified in Envoy's zstd decompressor implementation (ZstdDecompressorImpl). When zstd decompression is enabled, processing a specially crafted, highly compressed zstd payload can lead to massive memory allocation. An attacker can exploit this to cause severe memory exhaustion, potentially resulting in an Out-Of-Memory (OOM) kill and Denial of Service (DoS) for the Envoy proxy. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

What

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.23.0 until 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability has been identified in Envoy's zstd decompressor implementation (ZstdDecompressorImpl). When zstd decompression is enabled, processing a specially crafted, highly compressed zstd payload can lead to massive memory allocation. An attacker can exploit this to cause severe memory exhaustion, potentially resulting in an Out-Of-Memory (OOM) kill and Denial of Service (DoS) for the Envoy proxy. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

Why

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

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.23.0 until 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability has been identified in Envoy's zstd decompressor implementation (ZstdDecompressorImpl). When zstd decompression is enabled, processing a specially crafted, highly compressed zstd payload can lead to massive memory allocation. An attacker can exploit this to cause severe memory exhaustion, potentially resulting in an Out-Of-Memory (OOM) kill and Denial of Service (DoS) for the Envoy proxy. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

Why

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

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

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.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Improper Handling of Highly Compressed Data (Data Amplification) → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-409 ↗

CWE-409: Improper Handling of Highly Compressed Data (Data Amplification). The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-409Public exploit reference
A

Official authority intelligence

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

BSI · German · WID-SEC-W-2026-2048Google Cloud Service Mesh und Envoy Proxy: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Google Cloud Service Mesh und Envoy Proxy ausnutzen, um einen Denial-of-Service-Zustand zu verursachen, Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen oder andere, nicht näher bezeichnete Angriffe durchzuführen.

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
openshift-service-mesh/proxyv2-rhel9 as a component of OpenShift Service Mesh 2
Fixed
registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:59fa6f408b345a25d7e9dd12cf79c5e56cae7a7c2d814ef32512346021485060_amd64 as a component of Red Hat OpenShift Service Mesh 3.0; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:cd1e969fed2cc48c6b2b2e911164bba8294bce35b5e386d64729296aed5a31e7_s390x as a component of Red Hat OpenShift Service Mesh 3.0; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:e1de2591216c2b907756cb1589e5257469e358ec26fd54355a9e2adb492854fd_ppc64le as a component of Red Hat OpenShift Service Mesh 3.0; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:e2de4e2eaa221b5942369955da3a1a0eaf3076ef444dafc36739481ef0c583ef_arm64 as a component of Red Hat OpenShift Service Mesh 3.0; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:94921265f210e84d79eeba8821c4527e81c36bfc7ce98f0cc8d64b44cbeef7a0_amd64 as a component of Red Hat OpenShift Service Mesh 3.1; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:aac19045406a2c70e71543728fd4f31df14ad9cd6836ffacbeb3218ad3d96e0c_arm64 as a component of Red Hat OpenShift Service Mesh 3.1; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:b4e81569b945540d729d2d35519eff01bbc865afdbe2343a692dedabca14f84f_ppc64le as a component of Red Hat OpenShift Service Mesh 3.1; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:d287bfac8a2858a046ef4f19dad906e158292843d445b94da70513112098e327_s390x as a component of Red Hat OpenShift Service Mesh 3.1; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:a9893f3cced5ab9bafa20ae5f920cba27e852cc5e9f28b01a349a21d8f1ea63f_s390x as a component of Red Hat OpenShift Service Mesh 3.2; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:d689694c5d1d84b84b75ca31fd13811e8e3ad18f7d128ebf3c3f971244deb146_ppc64le as a component of Red Hat OpenShift Service Mesh 3.2; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:e0f294f32e31dfc832ff5a1ce8e373bbed467a1e91fc74108e9a528dbc11f541_amd64 as a component of Red Hat OpenShift Service Mesh 3.2; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:f7f79b5a5021d6c045c5eba12ff8d52629b959bb5e38ebb54ac510286a354049_arm64 as a component of Red Hat OpenShift Service Mesh 3.2; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:09292f6545b2e6619bbbd267024fa4f9c6c8b760e53cfc2833eb54d9f453453e_ppc64le as a component of Red Hat OpenShift Service Mesh 3.3; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:2822039fd4beacdce9ba55663107db291846050ffae0a59c4a8059b81a2a99bd_arm64 as a component of Red Hat OpenShift Service Mesh 3.3; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:4938aa51aff7c6cd248fa954e00bc414221f4236001fc4b032305b33ce3cfa12_s390x as a component of Red Hat OpenShift Service Mesh 3.3; registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9@sha256:9eba1d3fbc947bb0fe267818fc7a5e06bf403004a045e80c65b2592a7bd06da4_amd64 as a component of Red Hat OpenShift Service Mesh 3.3
Action
See Red Hat OpenShift Service Mesh 3.0.14 documentation at https://docs.redhat.com/en/documentation/red_hat_openshift_service_mesh/3.0
Workaround
A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04

Evidence and provenance

Published 26 Jun 2026 · Last source change 26 Jun 2026, 18:31 UTC · CWE-409 · Improper Handling of Highly Compressed Data (Data Amplification)

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-2026-39820
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

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

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Mitigation reference recorded
ENISA EUVD · EUVD-2026-39820↗Vendor CSAF · Red Hat Product Security↗Public exploit reference↗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-2026-48044 · cve.blacktree.nl