Security readout for executives and security teams
Plain-English summary
A malicious TAR archive can bypass Python’s intended extraction protections by creating symbolic links that point outside the chosen destination. This breaks the expected containment boundary and may expose sensitive files. Risk exists only where applications extract untrusted archives through the affected tarfile interfaces.
Executive priority
Treat this as urgent where public or otherwise untrusted TAR files are processed. Elsewhere, complete exposure inventory promptly and remediate within the normal high-severity window. The absence of confirmed exploitation lowers immediate incident-response urgency, but it does not reduce risk for exposed extraction services.
Technical view
CVE-2025-4138 affects CPython tarfile extraction using TarFile.extractall() or TarFile.extract() with filter="data" or filter="tar". Crafted symlink targets can escape the destination directory, and some file metadata can be modified. Python 3.14’s default "data" filter is also affected. The supplied CVSS 3.1 score is 7.5, emphasizing confidentiality impact.
Likely exposure
Exposure is concentrated in applications that extract untrusted TAR archives using the affected calls and filters. Python 3.14 users relying on the new default filter may also be exposed. Applications that do not process untrusted TAR archives through these paths are unlikely to be affected.
Exploitation context
The supplied record does not list this CVE in KEV and provides no evidence of active exploitation. Its CVSS vector describes network reachability, low complexity, no required privileges, and no user interaction, but practical exploitation still requires an application to extract an attacker-controlled archive through an affected path.
Researcher notes
The structured affected data names specific CPython versions but does not provide clear fixed-release boundaries; its default status is unaffected. Avoid generalizing entire release branches without consulting vendor guidance. Review the linked issue, patch, commits, and mitigation for branch-specific behavior. Source-distribution installation is not materially worsened because builds already permit arbitrary code execution.
Mitigation direction
- Inventory applications using TarFile.extractall() or TarFile.extract() on untrusted archives.
- Upgrade affected CPython runtimes to fixed releases identified by Python’s security guidance.
- Until upgraded, avoid processing untrusted TAR archives through affected extraction paths.
- Review the cited vendor mitigation before implementing temporary application-level controls.
Validation and detection
- Record Python versions for every workload that extracts untrusted TAR archives.
- Search application code for affected extraction calls, filters, and trust boundaries.
- Confirm fixed-version applicability against the Python advisory because this bundle lacks precise fixed-release mapping.
- Run non-destructive regression tests confirming extraction cannot create symlink targets outside the destination.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-22: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-4138 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6PSFVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/python/cpython/issues/135034CVE reference, PSF · issue-tracking
- https://github.com/python/cpython/pull/135037CVE reference, PSF · patch
- https://mail.python.org/archives/list/security-announce@python.org/thread/MAXIJJCUUMCL7ATZNDVEGGHUMQMUUKLG/CVE reference, PSF · vendor-advisory
- https://github.com/python/cpython/commit/3612d8f51741b11f36f8fb0494d79086bac9390aCVE reference, PSF · patch
- https://github.com/python/cpython/commit/9e0ac76d96cf80b49055f6d6b9a6763fb9215c2aCVE reference, PSF · patch
- https://gist.github.com/sethmlarson/52398e33eff261329a0180ac1d54f42fCVE reference, PSF · mitigation
- https://github.com/python/cpython/commit/19de092debb3d7e832e5672cc2f7b788d35951daCVE reference, PSF · patch
- https://github.com/python/cpython/commit/aa9eb5f757ceff461e6e996f12c89e5d9b583b01CVE reference, PSF · patch
- https://github.com/python/cpython/commit/28463dba112af719df1e8b0391c46787ad756dd9CVE reference, PSF · patch
- https://github.com/python/cpython/commit/4633f3f497b1ff70e4a35b6fe2c907cbe2d4cb2eCVE reference, PSF · patch
- https://github.com/python/cpython/commit/9c1110ef6652687d7c55f590f909720eddde965aCVE reference, PSF · patch
- https://github.com/python/cpython/commit/dd8f187d0746da151e0025c51680979ac5b4cfb1CVE reference, PSF · patch
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.