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CVE Record

CVE-2025-8291: ZIP64 End of Central Directory (EOCD) Locator record offset not checked

The 'zipfile' module would not check the validity of the ZIP64 End of Central Directory (EOCD) Locator record offset value would not be used to locate the ZIP64 EOCD record, instead the ZIP64 EOCD record would be assumed to be the previous record in the ZIP archive. This could be abused to create ZIP archives that are handled differently by the 'zipfile' module compared to other ZIP implementations. Remediation maintains this behavior, but checks that the offset specified in the ZIP64 EOCD Locator record matches the expected value.

MediumCVSS 4.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Python’s ZIP handling could accept a specially crafted ZIP64 archive whose internal location metadata is inconsistent. Another ZIP tool may interpret the same archive differently, potentially allowing content to pass one validation stage but behave differently later. The documented impact is limited to integrity, not confidentiality or availability.

Executive priority

Prioritize remediation on internet-facing upload, scanning, package-processing, and document-ingestion workflows. For systems processing only trusted archives, handle through normal patching. Escalate where one component validates archives before another parser performs a security-sensitive action.

Technical view

CPython’s zipfile module assumed the ZIP64 End of Central Directory record immediately preceded its locator and did not validate the locator’s recorded offset. Crafted archives could therefore create parser differentials between zipfile and other ZIP implementations. The remediation preserves record-location behavior while requiring the recorded offset to match the expected value.

Likely exposure

Exposure is most likely where applications process attacker-supplied ZIP64 archives, especially pipelines using different ZIP parsers for validation and consumption. The bundle identifies CPython version entries but does not provide clear affected ranges or fixed release numbers, so deployments require comparison with Python’s advisory and patch history.

Exploitation context

The CVSS vector permits network delivery but requires user interaction. The bundle includes public Google security research tagged as exploit material, but provides no evidence of active exploitation, and the CVE is not identified as KEV. Practical risk depends on whether inconsistent archive interpretation crosses a security or trust boundary.

Researcher notes

CWE-1285 and CVSS 4.3 characterize an input-validation weakness with low integrity impact. The central issue is parser differential behavior, not a documented standalone code-execution primitive. Exact affected and fixed release boundaries remain unclear in the supplied data; verify them against the vendor advisory and referenced branch commits.

Mitigation direction

  • Apply a vendor-supported CPython release or backport containing the referenced offset-validation fix.
  • Consult Python’s security advisory for branch-specific remediation because fixed release numbers are absent from the bundle.
  • Temporarily restrict or quarantine untrusted ZIP64 archives in security-sensitive processing pipelines.
  • Avoid relying on one ZIP parser’s acceptance as approval for another component to consume the archive.

Validation and detection

  • Inventory services, tools, and automation using Python zipfile with externally supplied archives.
  • Record deployed Python versions and confirm the vendor fix or an equivalent backport is present.
  • Test that archives with inconsistent ZIP64 locator offsets are rejected safely after remediation.
  • Review multi-parser workflows for validation and extraction differences at trust boundaries.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-1285: Exact CWE lookup

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cve · low confidence lookup

CVE-2025-8291 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.3 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Official CVE source material

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.

1CVSS vectors
3Timeline events
1ADP providers
13Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
4.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N2.81.4PSF

Vulnerability scoring details

Base CVSS 3.1 score

4.3Medium
CVSS 3.1 vector shape for CVE-2025-8291Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Python Software FoundationCPython0, 3.10.0, 3.11.0, 3.12.0, 3.13.0, 3.14.0unaffected
Weakness

CWE details

CWE-1285

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-1285 · source CWE mapping

Improper Validation of Specified Index, Position, or Offset in Input

Improper Validation of Specified Index, Position, or Offset in Input represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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