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Stack-based Buffer OverflowWeakness · CWE-121

CVE-2026-42996

CRITICAL · 10.0 CVSS v4.0 Published 2026-05-01
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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
JS8Call through 2.3.1 and JS8Call-improved before 3.0 have a stack-based buffer overflow via a radio transmission of @APRSIS GRID followed by a long Maidenhead locator. This occurs in grid2deg in APRSISClient.cpp.

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

A stack-based buffer overflow vulnerability exists in the grid2deg function within APRSISClient.cpp of JS8Call (versions 2.3.1 and prior) and JS8Call-improved (versions before 3.0). The vulnerability is triggered by processing a radio transmission containing @APRSIS GRID followed by an excessively long Maidenhead locator string, causing overflow of a fixed-size stack buffer.

MitigationUpgrade to JS8Call version 2.3.2 or later, or JS8Call-improved version 3.0 or later to obtain the patched version of the grid2deg function with proper bounds checking.

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

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
Authentication
Y
User interaction
None
Scope
P

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:P/AU:Y/R:U/V:D/RE:M/U:Green

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. Check if JS8Call is installed
    Look for the JS8Call executable or installation directory. On Windows, check Program Files for JS8Call folder; on Linux, check /usr/local/bin or ~/.local/bin for js8call or js8call-improved.
    Affected if JS8Call or JS8Call-improved software is present on the system
  2. Determine installed JS8Call version
    Launch JS8Call and check the Help > About menu, or check the application executable version properties. For command-line, run 'js8call --version' if available.
    Affected if Version is 2.3.1 or prior for JS8Call, or below 3.0 for JS8Call-improved
  3. Verify APRSIS functionality is enabled
    Check if the APRS-IS reporting feature is configured in JS8Call settings. Look for APRSIS enabled status in the application settings or configuration files.
    Affected if APRSIS/APRS-IS reporting is enabled and the application processes APRS messages from radio transmissions
  4. Check if system processes incoming radio transmissions
    Verify the application is configured to receive and process incoming radio transmissions containing APRSIS commands. Review any logging or message handling configuration.
    Affected if The application is actively receiving and processing radio transmissions that could contain @APRSIS GRID messages

A user is affected if JS8Call version 2.3.1 or earlier (or JS8Call-improved below 3.0) is installed with APRSIS functionality enabled to process incoming radio transmissions.

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
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Upgrade to JS8Call version 2.3.2 or later, or JS8Call-improved version 3.0 or later to obtain the patched version of the grid2deg function with proper bounds checking.

Recommended fix Moderate confidence

JS8Call-improved version 3.0 or later (or JS8Call version >2.3.1 if available)

  1. 1. Identify which version of JS8Call software is currently installed (either JS8Call original or JS8Call-improved)
  2. 2. For JS8Call original users: upgrade to any version released after 2.3.1
  3. 3. For JS8Call-improved users: upgrade to version 3.0 or later
  4. 4. After upgrading, verify the grid2deg function in APRSISClient.cpp properly bounds-checks the Maidenhead locator input before processing
Caveat Users should verify any custom scripts or integrations that parse APRSIS GRID messages continue to function correctly after upgrade

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

Have this fixed 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
Get the patch applied

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,928.

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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-2026-42996 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
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  • Version or environment caveats, and links to real fixes
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