CVE-2025-4138Public exploitNetwork attack vector

Arbitrary symlink creation via unnormalized link targets

Published Jun 3, 2025 · Updated Jul 31, 2026

Path traversal in the CPython tarfile module allows remote attackers to create arbitrary symlinks outside the extraction directory via crafted archives. The data_filter function checks TarInfo.linkname without first normalizing internal parent-directory components, so a link target can pass the destination-boundary test with a different effective path. Exposure requires extracting an untrusted archive with TarFile.extract or TarFile.extractall using the data filter; the created symlink has the extracting process's filesystem access.

CVSS severity7.5
High
EPSS probability1.39%
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 the CPython tarfile module allows remote attackers to create arbitrary symlinks outside the extraction directory via crafted archives. The data_filter function checks TarInfo.linkname without first normalizing internal parent-directory components, so a link target can pass the destination-boundary test with a different effective path. Exposure requires extracting an untrusted archive with TarFile.extract or TarFile.extractall using the data filter; the created symlink has the extracting process's filesystem access.

The record

CVE
CVE-2025-4138
Published
Jun 3, 2025
Updated
Jul 31, 2026
Vendor
Python Software Foundation
Product
CPython
Classifications
CWE-22
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 3, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 31, 2026Record 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 <3.9.23
  2. Affected versionversion=3.10.0 <3.10.18
  3. Affected versionversion=3.11.0 <3.11.13
  4. Affected versionversion=3.12.0 <3.12.11
  5. Affected versionversion=3.13.0 <3.13.4
  6. Affected versionversion=3.14.0a1 <3.14.0b3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Python Software Foundation · CPythonversion=0 <3.9.23; version=3.10.0 <3.10.18; version=3.11.0 <3.11.13; version=3.12.0 <3.12.11; version=3.13.0 <3.13.4; version=3.14.0a1 <3.14.0b3

Published CVSS scores

7.5Python Software FoundationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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.

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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