CVE-2021-39208Network attack vector

Limited file write via unterminated destination path

Published Sep 16, 2021 · Updated Aug 4, 2024

Path traversal in Adam Hathcock SharpCompress before 0.29.0 allows remote authenticated users to write files outside an extraction directory. WriteEntryToDirectory checks that the resolved entry path starts with the resolved destination path, but fails to append a directory separator before comparison. The flaw is reachable when ExtractFullPath is enabled and the destination path lacks a trailing separator; attacker-controlled archive names can then create constrained sibling-path files.

CVSS severity4.3
Medium
EPSS probability1.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Adam Hathcock SharpCompress before 0.29.0 allows remote authenticated users to write files outside an extraction directory. WriteEntryToDirectory checks that the resolved entry path starts with the resolved destination path, but fails to append a directory separator before comparison. The flaw is reachable when ExtractFullPath is enabled and the destination path lacks a trailing separator; attacker-controlled archive names can then create constrained sibling-path files.

The record

CVE
CVE-2021-39208
Published
Sep 16, 2021
Updated
Aug 4, 2024
Vendor
Adam Hathcock
Product
SharpCompress
Classifications
CWE-22
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=< 0.29.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Adam Hathcock · SharpCompressversion=< 0.29.0

Published CVSS scores

4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:P/A:N

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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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