CVE-2023-39323Network attack vector

Arbitrary code execution via line directive bypass

Published Oct 5, 2023 · Updated Jun 12, 2025

Code injection in Google Cloud Go command before 1.20.9 and 1.21.0 through 1.21.1 allows attackers to execute code during go build via crafted source. The cmd/go parser accepts crafted //line directives that alter the apparent source path, bypassing checks that reject blocked //go:cgo_ compiler and linker flags. Exploitation requires attacker-controlled source containing the absolute path of its directive file and a build invocation, after which injected flags execute arbitrary code with the builder's privileges.

CVSS severity8.1
High
EPSS probability1.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in Google Cloud Go command before 1.20.9 and 1.21.0 through 1.21.1 allows attackers to execute code during go build via crafted source. The cmd/go parser accepts crafted //line directives that alter the apparent source path, bypassing checks that reject blocked //go:cgo_ compiler and linker flags. Exploitation requires attacker-controlled source containing the absolute path of its directive file and a build invocation, after which injected flags execute arbitrary code with the builder's privileges.

The record

CVE
CVE-2023-39323
Published
Oct 5, 2023
Updated
Jun 12, 2025
Vendor
Google Cloud
Product
Go command
Classifications
CWE-94, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 5, 2023CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 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 <1.20.9
  2. Affected versionversion=1.21.0-0 <1.21.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Go commandversion=0 <1.20.9; version=1.21.0-0 <1.21.2

Published CVSS scores

8.1CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1204.002Malicious File

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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