CVE-2024-53271Public exploitNetwork attack vector

Response mixup and disruption via duplicate completion

Published Dec 18, 2024 · Updated Dec 18, 2024

HTTP/1.1 parsing in Envoy 1.31.0 through 1.31.4 or 1.32.0 through 1.32.2 allows attackers to mix responses and disrupt traffic via 1xx responses. BalsaParser::MessageDone processes completion twice after an early non-101 informational response instead of waiting for the first byte of the next message. The path requires delayed reset, an HTTP/1.1 keep-alive upstream, and a client request routed to an upstream that sends the informational response before its final response.

CVSS severity7.1
High
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

HTTP/1.1 parsing in Envoy 1.31.0 through 1.31.4 or 1.32.0 through 1.32.2 allows attackers to mix responses and disrupt traffic via 1xx responses. BalsaParser::MessageDone processes completion twice after an early non-101 informational response instead of waiting for the first byte of the next message. The path requires delayed reset, an HTTP/1.1 keep-alive upstream, and a client request routed to an upstream that sends the informational response before its final response.

The record

CVE
CVE-2024-53271
Published
Dec 18, 2024
Updated
Dec 18, 2024
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-670, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 18, 2024CVE publishedPublication date reported by the CVE source.
  2. Dec 18, 2024Record 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=>= 1.31.0, < 1.31.5
  2. Affected versionversion=>= 1.32.0, < 1.32.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Envoy Proxy · Envoyversion=>= 1.31.0, < 1.31.5; version=>= 1.32.0, < 1.32.3

Published CVSS scores

7.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H

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 exploitPublished

Weakness, pattern, technique

CWE-670Always-Incorrect Control Flow Implementation
T1499.004Application or System Exploitation

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo