CVE-2021-30717Public exploitNetwork attack vector

Code execution via SMB directory query overflow

Published Sep 8, 2021 · Updated Aug 3, 2024

Memory corruption in Apple macOS smbx before Big Sur 11.4 allows remote authenticated users to execute code through crafted SMB directory queries. In smbd's smb2_dispatch_query_directory path, a failed UTF-16 conversion is negated and sign-extended into an oversized index, causing a one-byte out-of-bounds stack write. An authenticated SMB session and enabled SMB file sharing are required; the corrupted stack pointer can crash smbd or redirect execution in that service's context.

CVSS severity7.5
High
EPSS probability2.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Apple macOS smbx before Big Sur 11.4 allows remote authenticated users to execute code through crafted SMB directory queries. In smbd's smb2_dispatch_query_directory path, a failed UTF-16 conversion is negated and sign-extended into an oversized index, causing a one-byte out-of-bounds stack write. An authenticated SMB session and enabled SMB file sharing are required; the corrupted stack pointer can crash smbd or redirect execution in that service's context.

The record

CVE
CVE-2021-30717
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
macOS
Classifications
CWE-787, T1210
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=unspecified <11.4
  2. Affected versionversion=unspecified <2021

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Apple · macOSversion=unspecified <11.4; version=unspecified <2021

Published CVSS scores

7.5Cisco TalosCVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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-787Out-of-bounds Write
T1210Exploitation of Remote Services

Public exploit references

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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