CVE-2026-53716: 
Wolfi vulnerability analysis and mitigation

CVE-2026-53716 is an unbounded gzip decompression vulnerability ("zip bomb") in Envoy Gateway's Wasm HTTP fetcher that allows a low-privileged tenant to trigger memory exhaustion in the shared controller process, causing a persistent cross-tenant control-plane denial of service. It affects Envoy Gateway versions prior to 1.7.4 and versions 1.8.0-rc.0 through 1.8.0 (prior to 1.8.1). The vulnerability was disclosed on June 5, 2026, via a GitHub Security Advisory, with CVE assignment and NVD publication following on September 14, 2026. It carries a CVSS v3.1 base score of 6.5 (Medium) (GitHub Advisory).

The root cause is classified as CWE-789 (Memory Allocation with Excessive Size Value). The vulnerable function getFileFromGZ in internal/wasm/httpfetcher.go calls io.ReadAll on a gzip.Reader without imposing any limit on the decompressed output size. While the compressed input is capped at 256 MiB, this cap does not constrain the expanded data; a tenant-controlled EnvoyExtensionPolicy.spec.wasm[].code.http.url can point to an attacker-hosted gzip bomb (e.g., ~10 MiB compressed expanding to ~10 GiB), forcing a multi-gigabyte heap allocation in the shared controller. The optional sha256 integrity check is performed only after decompression, and no operator-level Wasm URL allowlist exists, so all candidate guards execute either before buffering or after the damage is done. The attack requires only network access and low privileges (the ability to create an EnvoyExtensionPolicy resource) (GitHub Advisory).

Successful exploitation causes an out-of-memory (OOM) termination of the shared Envoy Gateway controller process. Because the malicious EnvoyExtensionPolicy custom resource persists in Kubernetes, the controller restarts, re-reconciles the same resource, and is repeatedly OOM-killed, creating a persistent crash loop. This results in a cross-tenant control-plane outage — all tenants sharing the controller lose gateway management functionality — with no confidentiality or integrity impact, but complete availability loss for the control plane (GitHub Advisory).

No public proof-of-concept exploit code or in-the-wild exploitation has been reported. The EPSS score is approximately 0.685%, indicating a low probability of near-term exploitation. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. NVD's SSVC assessment classifies exploitation as "none" and the attack as non-automatable, reflecting the requirement for a tenant with EnvoyExtensionPolicy creation privileges in a multi-tenant Envoy Gateway deployment (GitHub Advisory).

1. Gain tenant access: Obtain credentials or a Kubernetes service account with permission to create EnvoyExtensionPolicy resources in a namespace managed by a vulnerable Envoy Gateway controller (versions < 1.7.4 or 1.8.0-rc.0–1.8.0).
2. Prepare a gzip bomb: Host a crafted gzip-compressed file at an attacker-controlled URL. A ~10 MiB gzip-of-zeros that decompresses to ~10 GiB is sufficient to exhaust controller memory.
3. Create a malicious EnvoyExtensionPolicy: Apply a Kubernetes manifest referencing the gzip bomb URL in spec.wasm[].code.http.url, optionally omitting the sha256 field (since the check occurs post-decompression anyway).
4. Trigger decompression: The Envoy Gateway controller fetches and decompresses the Wasm payload via getFileFromGZ, allocating multi-gigabyte memory with no output-size bound.
5. Achieve persistent DoS: The controller process is OOM-killed by the kernel. On restart, it re-reconciles the persistent custom resource and is killed again, creating a crash loop that denies control-plane service to all tenants (GitHub Advisory).

• Kubernetes Events/Logs: Repeated OOMKilled events for the envoy-gateway controller pod; controller pod restart count rapidly increasing; Kubernetes events showing OOMKilled as the termination reason.
• Controller Logs: Log entries in the Envoy Gateway controller showing repeated fetch attempts to the same external Wasm URL followed by process termination; absence of normal reconciliation log output.
• Network: Outbound HTTP/HTTPS requests from the controller pod to an unexpected or external URL serving a large compressed file, particularly if the response is small but decompression stalls or consumes excessive memory.
• Kubernetes Resources: Presence of an EnvoyExtensionPolicy resource with a spec.wasm[].code.http.url pointing to an external or unfamiliar host, especially without a sha256 field set (GitHub Advisory).

Upgrade Envoy Gateway to version 1.7.4 (for the 1.7.x branch) or 1.8.1 (for the 1.8.x branch), which introduce a decompressed-output size limit in getFileFromGZ. Patches were merged via PRs #9171, #9172, and #9173. As a workaround prior to patching, operators should restrict or audit which tenants can create EnvoyExtensionPolicy resources using Kubernetes RBAC, and consider implementing network policies to limit outbound HTTP access from the controller pod to trusted Wasm artifact registries (GitHub Advisory).