CVE-2023-35945Network attack vector

Service interruption via leaked HTTP/2 request state

Published Jul 13, 2023 · Updated Oct 31, 2024

Memory exhaustion in Envoy allows remote attackers controlling an upstream server to interrupt service through crafted HTTP/2 frames. After RST_STREAM frees capacity and submits another request, GOAWAY handling returns before releasing the pending header map and nghttp2 bookkeeping structure. Repeating the unauthenticated upstream frame sequence leaks memory until the Envoy process terminates, without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability1.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory exhaustion in Envoy allows remote attackers controlling an upstream server to interrupt service through crafted HTTP/2 frames. After RST_STREAM frees capacity and submits another request, GOAWAY handling returns before releasing the pending header map and nghttp2 bookkeeping structure. Repeating the unauthenticated upstream frame sequence leaks memory until the Envoy process terminates, without reported data disclosure or modification.

The record

CVE
CVE-2023-35945
Published
Jul 13, 2023
Updated
Oct 31, 2024
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-459, CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 13, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 31, 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=>= 1.23.0, < 1.23.11
  2. Affected versionversion=>= 1.24.0, < 1.24.9
  3. Affected versionversion=>= 1.25.0, < 1.25.8
  4. Affected versionversion=>= 1.26.0, < 1.26.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Envoy Proxy · Envoyversion=>= 1.23.0, < 1.23.11; version=>= 1.24.0, < 1.24.9; version=>= 1.25.0, < 1.25.8; version=>= 1.26.0, < 1.26.3

Published CVSS scores

7.5GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-459Incomplete Cleanup
CWE-400Uncontrolled Resource Consumption
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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