# CVE-2026-127125: NULL pointer dereference when a response fragment is not acknowledged

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

P-Net before 1.0.4 aborts the Application Relationship of an RPC session when a fragment of a response has been resent without being acknowledged, without checking that the session has an Application Relationship. A request for an existing Application Relationship that is sent on another activity than its Connect, and gets a fragmented response, is handled on a session without one. If the response is not acknowledged, a NULL pointer is dereferenced and the device crashes. A conformant IO-controller does not send such requests. The attacker must have observed the AR UUID of an established Application Relationship and requires ADJACENT network access.

## Remediation

- fix: Upgrade to P-Net 1.0.4 or later. (source: CNA: rt-labs)

## Affected products and versions

- RT-Labs / P-Net: ≥ 0; < 1.0.4 (affected, semver). Source: CNA: rt-labs

## Severity and prioritization

- CVSS 4.0: 6 (medium); CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: rt-labs

- CVSS 4.0: 6 (medium); CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/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:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: 4b71179a-3b92-4a9d-b9fc-af8b8ed579ee

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-476

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://rt-labs.com/wp-content/uploads/2026/11/RRTL-261109-01.pdf (CNA: rt-labs)

- https://rt-labs.com/wp-content/uploads/2026/11/RRTL-261109-01.pdf (4b71179a-3b92-4a9d-b9fc-af8b8ed579ee)

## Provenance

- CNA: rt-labs: https://www.cve.org/CVERecord?id=CVE-2026-127125; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-127125; retrieved 2026-11-13; source updated 2026-11-13

Revision: 366e6c13b3f1d0493a5bb93da1d61e7f15a77c2e8d9a87606416975d16c39097

Canonical: https://y2.dev/cve/CVE-2026-127125

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