CVE-2023-39326Network attack vector

Denial of service via chunk-extension amplification

Published Dec 6, 2023 · Updated Feb 13, 2025

Resource exhaustion in Go standard library net/http/internal before 1.20.12 and 1.21.0-0 through 1.21.4 allows remote attackers to interrupt services. The chunkedReader.Read and chunkedReader.beginChunk routines discard arbitrarily large chunk-extension metadata without bounding encoded overhead against returned body bytes. Any HTTP request or response path that reads a chunked body is exposed; servers may automatically read roughly 1 GiB when handlers leave request bodies unread.

CVSS severity5.3
Medium
EPSS probability1.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Go standard library net/http/internal before 1.20.12 and 1.21.0-0 through 1.21.4 allows remote attackers to interrupt services. The chunkedReader.Read and chunkedReader.beginChunk routines discard arbitrarily large chunk-extension metadata without bounding encoded overhead against returned body bytes. Any HTTP request or response path that reads a chunked body is exposed; servers may automatically read roughly 1 GiB when handlers leave request bodies unread.

The record

CVE
CVE-2023-39326
Published
Dec 6, 2023
Updated
Feb 13, 2025
Vendor
Go standard library
Product
net/http/internal
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 6, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=0 <1.20.12
  2. Affected versionversion=1.21.0-0 <1.21.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go standard library · net/http/internalversion=0 <1.20.12; version=1.21.0-0 <1.21.5

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

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

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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