CVE-2021-21814Public exploit

Local code execution via out-of-bounds terminator write

Published Aug 13, 2021 · Updated Aug 3, 2024

Stack-based buffer overflow in AT&T Labs XMill 0.7 allows local users to execute code via a crafted command-line file pattern. The Windows HandleFileArg path parser derives an unchecked offset from filepattern, copies the path into the 400-byte fullpath stack buffer, and writes a null byte beyond that buffer. Exploitation requires low-privileged local access to invoke the Windows build; the overwrite can corrupt stack memory and redirect execution.

CVSS severity7.8
High
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in AT&T Labs XMill 0.7 allows local users to execute code via a crafted command-line file pattern. The Windows HandleFileArg path parser derives an unchecked offset from filepattern, copies the path into the 400-byte fullpath stack buffer, and writes a null byte beyond that buffer. Exploitation requires low-privileged local access to invoke the Windows build; the overwrite can corrupt stack memory and redirect execution.

The record

CVE
CVE-2021-21814
Published
Aug 13, 2021
Updated
Aug 3, 2024
Vendor
AT&T Labs
Product
XMill
Classifications
CWE-88, CWE-120, T1203
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 13, 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=AT&T Labs Xmill 0.7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

AT&T Labs · XMillversion=AT&T Labs Xmill 0.7

Published CVSS scores

7.8Cisco TalosCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS:3.1/AV:L/AC:L/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

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-88Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1203Exploitation for Client Execution

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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