What is the CVSS score of CVE-2026-47221?

CVE-2026-47221 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.4%.

Is there a patch available for CVE-2026-47221?

Yes, a patch is available for CVE-2026-47221. Update the affected software to the latest version immediately.

Envoy Proxy CVE-2026-47221

EUVD-2026-39823 HIGH

NULL Pointer Dereference (CWE-476)

2026-06-26 GitHub_M

Denial Of Service Null Pointer Dereference Envoy Red Hat Suse

7.5

CVSS 3.1 · NVD

Severity by source

Vendor (GitHub_M) PRIMARY

MEDIUM

qualitative

NVD

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

vuln.today AI

5.9 MEDIUM

Network-reachable and unauthenticated (AV:N/PR:N), but AC:H due to required non-default route configuration and upstream HTTP 303 response dependency; only availability is impacted.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

SUSE

HIGH

qualitative

Red Hat

5.9 MEDIUM

qualitative

Primary rating from Vendor (GitHub_M).

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Severity Changed

Jun 27, 2026 - 20:22 NVD

MEDIUM HIGH

CVSS changed

Jun 27, 2026 - 20:22 NVD

5.9 (MEDIUM) 7.5 (HIGH)

Patch available

Jun 26, 2026 - 19:02 EUVD

Analysis Generated

Jun 26, 2026 - 18:34 vuln.today

DescriptionNVD

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vulnerability when handling HTTP 303 (See Other) internal redirects for body-less non-GET/HEAD requests. When a POST, PUT, DELETE, or PATCH request without a body is sent to a route configured with internal redirect policy that includes 303 in redirect_response_codes, and the upstream responds with HTTP 303, the redirect handling code attempts to drain a request body buffer that was never allocated. This results in a segmentation fault that crashes the entire Envoy process. When route configured with internal_redirect_policy including 303 in redirect_response_codes and upstream must return HTTP 303 response, an unauthenticated attacker can exploit this to cause complete denial of service, terminating all active connections. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.

AnalysisAI

Null pointer dereference in Envoy's router filter crashes the entire proxy process, terminating all active connections, when body-less non-GET/HEAD requests (POST, PUT, DELETE, PATCH) encounter an upstream HTTP 303 response on a route configured with internal redirect policy. Affected versions span 1.18.0 through the fixes released in branches 1.35.13, 1.36.9, 1.37.5, and 1.38.3. An unauthenticated remote attacker who can influence upstream response codes or reach a vulnerable route configuration can cause complete denial of service; no public exploit identified at time of analysis and no CISA KEV listing.

Technical ContextAI

Envoy (CPE: cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*) is a widely deployed cloud-native L7 proxy and service mesh sidecar, commonly used with Istio and Kubernetes. The router filter supports an internal redirect policy that allows Envoy to internally re-process responses with specific redirect codes (e.g., 301, 302, 303) rather than forwarding them to the client. CWE-476 (NULL Pointer Dereference) describes the root cause: when a POST, PUT, DELETE, or PATCH request arrives without a request body, no body buffer is allocated; however, when the upstream returns HTTP 303 and the redirect handling path is triggered, the code unconditionally attempts to drain that body buffer. Dereferencing the null pointer causes a segmentation fault that kills the entire Envoy worker process - not just the single connection - making this a process-level crash rather than a per-stream error.

RemediationAI

Upgrade Envoy to one of the patched releases: 1.35.13, 1.36.9, 1.37.5, or 1.38.3, selecting the version that matches the currently deployed release branch. Vendor-released patches are confirmed via GitHub Security Advisory GHSA-rcff-gw58-pjpr at https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjpr. If an immediate upgrade is not possible, the targeted workaround is to remove 303 from the redirect_response_codes list in all internal_redirect_policy configurations, which prevents the vulnerable code path from being triggered entirely; note that this changes application-level redirect behavior and should be validated against upstream service contracts. Alternatively, disabling internal_redirect_policy entirely on routes exposed to untrusted or external traffic eliminates the attack surface at the cost of losing redirect-following behavior for those routes.