CVE-2021-42374Public exploit

Heap disclosure and applet crash via LZMA input

Published Nov 15, 2021 · Updated Nov 3, 2025

Out-of-bounds read in BusyBox before 1.34.0 allows local users to disclose heap data or crash an applet via crafted LZMA input. In unpack_lzma_stream, a user-controlled dictionary size can leave a wrapped buffer position negative after one adjustment, and buffer[pos] then reads before the heap buffer. The user must cause an LZMA stream to be decompressed by unlzma or another applet with seamless LZMA support; leaked bytes can enter decompressed output, while a crash normally interrupts only that applet process.

CVSS severity5.3
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in BusyBox before 1.34.0 allows local users to disclose heap data or crash an applet via crafted LZMA input. In unpack_lzma_stream, a user-controlled dictionary size can leave a wrapped buffer position negative after one adjustment, and buffer[pos] then reads before the heap buffer. The user must cause an LZMA stream to be decompressed by unlzma or another applet with seamless LZMA support; leaked bytes can enter decompressed output, while a crash normally interrupts only that applet process.

The record

CVE
CVE-2021-42374
Published
Nov 15, 2021
Updated
Nov 3, 2025
Vendor
BusyBox
Product
BusyBox
Classifications
CWE-125, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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=unspecified <1.34.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

BusyBox · BusyBoxversion=unspecified <1.34.0

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
5.3NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/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 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-125Out-of-bounds Read
T1005Data from Local System

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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