CVE-2023-35943Public exploitNetwork attack vector

Proxy crash via stale Origin header pointer

Published Jul 25, 2023 · Updated Oct 24, 2024

Use-after-free in Envoy's HTTP CORS filter allows remote authenticated users to crash affected proxy releases via Origin removal. decodeHeaders retains a pointer to the Origin header after configured request processing deletes it, and encodeHeaders dereferences the stale pointer. Exploitation requires the CORS filter and request_headers_to_remove: origin configuration; the resulting segfault interrupts the proxy service.

CVSS severity6.3
Medium
EPSS probability0.66%
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

Use-after-free in Envoy's HTTP CORS filter allows remote authenticated users to crash affected proxy releases via Origin removal. decodeHeaders retains a pointer to the Origin header after configured request processing deletes it, and encodeHeaders dereferences the stale pointer. Exploitation requires the CORS filter and request_headers_to_remove: origin configuration; the resulting segfault interrupts the proxy service.

The record

CVE
CVE-2023-35943
Published
Jul 25, 2023
Updated
Oct 24, 2024
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-416, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 25, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 24, 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=< 1.23.12
  2. Affected versionversion=>= 1.24.0, < 1.24.10
  3. Affected versionversion=>= 1.25.0, < 1.25.9
  4. Affected versionversion=>= 1.26.0, < 1.26.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Envoy Proxy · Envoyversion=< 1.23.12; version=>= 1.24.0, < 1.24.10; version=>= 1.25.0, < 1.25.9; version=>= 1.26.0, < 1.26.4

Published CVSS scores

6.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:H
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
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