CVE-2021-27347Public exploit

Process crash via premature multithreaded deallocation

Published Jun 10, 2021 · Updated Aug 3, 2024

Use after free in lrzip 0.631 allows local users to crash the lrzip process by testing a crafted compressed file. close_stream_in frees stream and thread structures while a decompression worker can still write through them in lzma_decompress_buf. Processing the file with multithreaded decompression and winning the race triggers a segmentation fault that interrupts only the invoked command-line process.

CVSS severity5.5
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use after free in lrzip 0.631 allows local users to crash the lrzip process by testing a crafted compressed file. close_stream_in frees stream and thread structures while a decompression worker can still write through them in lzma_decompress_buf. Processing the file with multithreaded decompression and winning the race triggers a segmentation fault that interrupts only the invoked command-line process.

The record

CVE
CVE-2021-27347
Published
Jun 10, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 10, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P

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.

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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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1204.002User Execution: Malicious File

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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