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Open Cascade TechnologyApplication · Opencascade

CVE-2026-42476

HIGH · 7.1 CVSS v3.1 Published 2026-05-01
Fix available
A fix is available. Upgrade to after 7.9.3 or later.
See remediation →
74/100
Remediation priority · Elevated
No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Two heap-based out-of-bounds read vulnerabilities in the STL ASCII file parser in Open CASCADE Technology (OCCT) V8_0_0_rc5 exist in RWStl_Reader::ReadAscii because buffers returned by Standard_ReadLineBuffer::ReadLine() are not properly length-validated before strncasecmp or direct byte access. User-assisted attackers can trigger these issues by persuading a victim to open a crafted STL file with extremely short lines, resulting in a denial of service or possible information disclosure.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Heap-based out-of-bounds read vulnerabilities in Open CASCADE Technology's STL ASCII parser (RWStl_Reader::ReadAscii) where buffers from Standard_ReadLineBuffer::ReadLine() lack proper length validation before strncasecmp() calls and direct byte access. Crafted STL files with extremely short lines trigger these OOB reads.

MitigationImplement bounds checking: validate buffer lengths before strncasecmp and any direct byte access operations in RWStl_Reader::ReadAscii. Reject or properly handle STL files with lines shorter than expected minimum lengths.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Open Cascade TechnologyApplication
Affected:<= 7.9.3= 8.0.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Open CASCADE Technology version
    Check the installed version of Open CASCADE Technology library (e.g., via package manager, file version info, or application's dependency list). Compare against affected versions: <= 7.9.3 or = 8.0.0.
    Affected if Installed version is 7.9.3 or earlier, or exactly 8.0.0
  2. Confirm STL ASCII parsing is in use
    Inspect application code or configuration to determine if RWStl_Reader::ReadAscii or the STL file reading module is invoked. Look for calls to functions that read STL files in ASCII format.
    Affected if The application parses STL files using Open CASCADE's STL reader module
  3. Verify input source accepts STL files
    Check if the application or system accepts user-supplied or externally sourced STL files (e.g., file upload, import feature, or CAD file processing pipeline).
    Affected if STL files from untrusted sources can be processed by the vulnerable parser
  4. Confirm ASCII STL format handling
    Determine whether the application processes ASCII-formatted STL files (look for .stl files being read as text/ASCII rather than binary). The vulnerability triggers specifically with ASCII STL files containing extremely short lines.
    Affected if ASCII STL files are processed by the RWStl_Reader component

You are affected if you run Open CASCADE Technology version 7.9.3 or earlier (or exactly 8.0.0) and process ASCII STL files through the RWStl_Reader::ReadAscii parser, which lacks bounds checking on short input lines.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 7.9.3
Interim mitigation

Implement bounds checking: validate buffer lengths before strncasecmp and any direct byte access operations in RWStl_Reader::ReadAscii. Reject or properly handle STL files with lines shorter than expected minimum lengths.

Recommended fix Moderate confidence

Open Cascade Technology 7.9.4 or later (or 8.0.1+ if available)

  1. 1. Identify all deployed instances of Open Cascade Technology (OCCT) versions 7.9.3 or earlier, or version 8.0.0
  2. 2. Obtain the official patch or fixed release from Open CASCADE's official distribution channels (opencascade.com or their GitHub repository)
  3. 3. Before deployment, test the fixed version in a staging environment to verify compatibility with your application
  4. 4. Deploy the fixed version to production environments
  5. 5. Implement file type validation policies to restrict processing of untrusted STL files in applications using OCCT
Caveat Upgrade may introduce API changes; review OCCT release notes for breaking changes between 7.9.x/8.0.0 and the fixed version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Open Cascade Technology Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42476 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data