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FedoraOperating system · Fedoraproject

CVE-2020-28636

CRITICAL · 9.8 CVSS v3.1 Published 2021-03-04
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
A code execution vulnerability exists in the Nef polygon-parsing functionality of CGAL libcgal CGAL-5.1.1. An oob read vulnerability exists in Nef_S2/SNC_io_parser.h SNC_io_parser::read_sloop() slh->twin() An attacker can provide malicious input to trigger this vulnerability.

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 · moderate confidence

A critical out-of-bounds read vulnerability exists in CGAL 5.1.1's Nef polygon-parsing functionality, specifically in the SNC_io_parser::read_sloop() function within Nef_S2/SNC_io_parser.h when calling slh->twin(). Attackers can trigger arbitrary code execution by providing specially crafted malicious input to the affected parsing code.

MitigationIsolate or restrict processing of untrusted polygon/Nef input files; apply vendor patches or upgrade to a patched CGAL version when available; implement network-level controls to limit exposure of affected parsing services.

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
FedoraOperating system
Affected:= 33= 34
Debian LinuxOperating system
Affected:= 9.0= 10.0
Computational Geometry Algorithms LibraryApplication
Affected:= 5.1.1

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 CGAL library version
    Run 'rpm -q cgal' on Fedora or 'dpkg -l libcgal-dev' on Debian to check installed CGAL package version. If CGAL is used as a linked library in a custom application, check the application's dependency list using 'ldd <executable>' or review build documentation for the CGAL version referenced.
    Affected if The installed CGAL version is exactly 5.1.1 (the specific version listed as affected).
  2. Locate vulnerable header file
    Search for the file SNC_io_parser.h in the system: 'find /usr -name SNC_io_parser.h 2>/dev/null' or check within project source directories if CGAL is built from source.
    Affected if The file exists at a path containing 'Nef_S2/SNC_io_parser.h' and is part of a CGAL 5.1.1 installation.
  3. Identify applications using CGAL Nef parsing
    Review any deployed applications that process polygon, mesh, or geometric data files. Search application code for includes of CGAL headers, particularly 'Nef_2', 'Nef_3', or 'Nef_S2' namespaces. Check for usage of 'read_sloop' or 'SNC_io_parser' in source code.
    Affected if Any application uses CGAL's Nef polygon-parsing functionality to process input files.
  4. Check for exposed services processing untrusted geometry input
    Audit network-exposed services or APIs that accept polygon, mesh, or computational geometry files as input. Review logs or access patterns for .nef, .polygon, or related geometry file uploads.
    Affected if Any service accepts and processes untrusted polygon/Nef input files from external sources.
  5. Audit CGAL library linkage
    On systems with CGAL-using applications, run 'ldconfig -p | grep -i cgal' or check application binary dependencies to confirm CGAL is loaded at runtime.
    Affected if The CGAL library is actively loaded by any running application or service.

A system is affected if CGAL version 5.1.1 is installed AND any application or service uses it to parse untrusted polygon/Nef input files.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Isolate or restrict processing of untrusted polygon/Nef input files; apply vendor patches or upgrade to a patched CGAL version when available; implement network-level controls to limit exposure of affected parsing services.

Recommended fix Moderate confidence

CGAL 5.2 or later stable release (any version newer than the vulnerable 5.1.1)

  1. 1. Identify the CGAL library version currently installed in your system
  2. 2. Check if the installed version matches the vulnerable version CGAL-5.1.1
  3. 3. Upgrade CGAL to a version newer than 5.1.1 (e.g., 5.2 or later stable release)
  4. 4. After upgrading, verify the new version is correctly installed
  5. 5. Rebuild any applications that link against CGAL to ensure they use the updated library
  6. 6. Test that the Nef polygon-parsing functionality works correctly with the updated library
Caveat Minor API changes may exist between 5.1.1 and newer versions; review CGAL release notes for any breaking changes relevant to your application

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

Fix this in Fedora Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,580
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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-2020-28636 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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