CVE-2024-30255

published 2024-04-04

CVE-2024-30255: Envoy is a cloud-native, open source edge and service proxy. The HTTP/2 protocol stack in Envoy versions prior to 1.29.3, 1.28.2, 1.27.4, and 1.26.8 are…

Priority P2 62 high 7.5 CVSS 3.1

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

Envoy is a cloud-native, open source edge and service proxy. The HTTP/2 protocol stack in Envoy versions prior to 1.29.3, 1.28.2, 1.27.4, and 1.26.8 are vulnerable to CPU exhaustion due to flood of CONTINUATION frames. Envoy's HTTP/2 codec allows the client to send an unlimited number of CONTINUATION frames even after exceeding Envoy's header map limits. This allows an attacker to send a sequence of CONTINUATION frames without the END_HEADERS bit set causing CPU utilization, consuming approximately 1 core per 300Mbit/s of traffic and culminating in denial of service through CPU exhaustion. Users should upgrade to version 1.29.3, 1.28.2, 1.27.4, or 1.26.8 to mitigate the effects of the CONTINUATION flood. As a workaround, disable HTTP/2 protocol for downstream connections.

Affected

7 ranges

Vendor	Product	Version range	Fixed in
envoyproxy	envoy	< 1.26.8	1.26.8
envoyproxy	envoy	—	—
envoyproxy	envoy	—	—
envoyproxy	envoy	—	—
envoyproxy	envoy	>= 1.27.0 < 1.27.4	1.27.4
envoyproxy	envoy	>= 1.28.0 < 1.28.2	1.28.2
envoyproxy	envoy	>= 1.29.0 < 1.29.3	1.29.3

Detection & IOCs extracted from sources · hover to see the quote

• → Detect HTTP/2 CONTINUATION frame floods: look for a high volume of CONTINUATION frames sent within a single HTTP/2 stream without the END_HEADERS bit set, which is the core attack pattern for this CVE. ↗
• → Monitor for sustained CPU exhaustion on Envoy proxy instances — the attack consumes approximately 1 CPU core per 300 Mbit/s of malicious traffic, which can serve as a threshold for anomaly-based alerting. ↗
• → Flag unauthenticated remote connections sending large numbers of HTTP/2 CONTINUATION frames to Envoy listeners; the attacker does not need to authenticate to exploit this vulnerability. ↗

• · Workaround: disabling HTTP/2 for downstream connections on Envoy will prevent exploitation. Environments that cannot immediately patch should apply this configuration change. ↗
• · Affected Envoy versions are prior to 1.29.3, 1.28.2, 1.27.4, and 1.26.8. Detection and patching scope should cover all deployments running older versions across these release trains. ↗
• · After an attack ends, Envoy is expected to recover on its own — CPU exhaustion is transient, not persistent. Incident response should account for self-recovery without requiring a restart. ↗
• · Multiple Red Hat product packages embed the vulnerable Envoy component (e.g., lvms4/topolvm-rhel9, rhceph/rhceph-5-dashboard-rhel8, openshift-sandboxed-containers/osc-rhel8-operator). Detection and patching scope must include these downstream distributions. ↗

CVSS provenance

nvd v3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

vendor_redhat 5.3 MEDIUM

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