CVE-2024-30255

HTTP/2: CPU exhaustion due to CONTINUATION frame flood

HIGH

7.5

CVSS Score

Published: April 4, 2024 at 07:41 PM UTC

Updated: June 17, 2026 at 07:26 AM UTC

1 product affected across 1 vendorEnvoy

Using envoy by envoyproxy?

Get instant alerts when new vulnerabilities affect envoy - before attackers find them.

Real-time alertsTrack your software stackFree plan available

Start Free Sign In

Severity

HIGH7.5

Exploit prediction

EPSS 88%

SSVC

No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Envoy · Envoyproxy

95%

v < 1.26.8v < 1.27.4v < 1.28.2v < 1.29.31.27.0 ≤ v < 1.27.41.28.0 ≤ v < 1.28.21.29.0 ≤ v < 1.29.31.27.0 1.28.0 1.29.0

Affected range stops below 1.26.8, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.27.4, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.28.2, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.29.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/envoyproxy/envoy/security/advisories/GHSA-j654-3ccm-vfmm

References (4)

Mailing ListThird Party Advisory

Source: [email protected]

http://www.openwall.com/lists/oss-security/2024/04/03/16

Mailing List

Source: [email protected]

http://www.openwall.com/lists/oss-security/2024/04/05/3

x_refsource_CONFIRMPatchThird Party Advisory

Source: [email protected]

https://github.com/envoyproxy/envoy/security/advisories/GHSA-j654-3ccm-vfmm

Source: af854a3a-2127-422b-91ae-364da2661108

https://www.kb.cert.org/vuls/id/421644

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-390

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create account Sign in

Free plan, no card