CVE-2024-30255Network attack vector

CPU exhaustion via unlimited HTTP/2 CONTINUATION frames

Published Apr 4, 2024 · Updated Nov 4, 2025

Denial of service in affected Envoy releases allows remote attackers to exhaust CPU by flooding HTTP/2 CONTINUATION frames. Envoy's HTTP/2 codec continues accepting unlimited CONTINUATION frames without END_HEADERS after header-map limits are exceeded. Any untrusted HTTP/2 peer can consume about one CPU core per 300 Mbit/s, interrupting proxy service without authentication or user interaction.

CVSS severity5.3
Medium
EPSS probability87.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Envoy releases allows remote attackers to exhaust CPU by flooding HTTP/2 CONTINUATION frames. Envoy's HTTP/2 codec continues accepting unlimited CONTINUATION frames without END_HEADERS after header-map limits are exceeded. Any untrusted HTTP/2 peer can consume about one CPU core per 300 Mbit/s, interrupting proxy service without authentication or user interaction.

The record

CVE
CVE-2024-30255
Published
Apr 4, 2024
Updated
Nov 4, 2025
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-390, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 4, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.26.8
  2. Affected versionversion=< 1.26.8
  3. Affected versionversion=>= 1.27.0, < 1.27.4
  4. Affected versionversion=1.27.0 <1.27.4
  5. Affected versionversion=>= 1.28.0, < 1.28.2
  6. Affected versionversion=1.28.0 <1.28.2
  7. Affected versionversion=>= 1.29.0, < 1.29.3
  8. Affected versionversion=1.29.0 <1.29.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Envoy Proxy · Envoyversion=0 <1.26.8; version=< 1.26.8; version=>= 1.27.0, < 1.27.4; version=1.27.0 <1.27.4; version=>= 1.28.0, < 1.28.2; version=1.28.0 <1.28.2; version=>= 1.29.0, < 1.29.3; version=1.29.0 <1.29.3

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-390Detection of Error Condition Without Action
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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