FreeModbus LINUXTCP Port Off-by-One Global Buffer Overflow in xMBPortTCPPool()
Priority MEDIUM 46CWE-787Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · High
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool (demo/LINUXTCP/port/porttcp.c). The check uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00501 43rd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| cwalter-at | FreeModbus | all versions | — | No fix listed | CNA |
- FreeModbus Vendorcwalter-at Affected all versions Fixed in — No fix listed CNA
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2026-71263
- 2026-10-03 Alias added: GHSA-cjvm-2pqq-6v6h
References
Sources
- CVE-2026-71263 · CVE Program
- CVE-2026-71263 · NVD
- FIRST EPSS
- GHSA-cjvm-2pqq-6v6h · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences