TI-2026-20659 Aliases CVE-2026-25551 GHSA-g42f-xxvf-qj27

Seagull Software BarTender Deserialization Privilege Escalation via .NET Remoting Service

HIGH 72CWE-502Published 2026-06-04 · Updated 2026-09-02

Key facts

Attack vector: Local
Privileges required: Low
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-502.

Summary

Seagull Software BarTender 2021 R1 through 12.0.1 contains an insecure deserialization vulnerability that allows low-privileged local users to escalate privileges. The DataServiceSingleton .NET Remoting endpoint is bound to localhost on TCP port 7375 via BtSystem.Service.exe, limiting the attack surface to local access only. The endpoint is configured with BinaryServerFormatterSinkProvider and TypeFilterLevel set to Full. A low-privileged local attacker can send YSoSerial.NET-generated BinaryFormatter payloads to the localhost-bound endpoint to achieve code execution as NT AUTHORITY\\\\SYSTEM. The vulnerability was corrected in BarTender 12.1, released on August 14, 2026. Users should upgrade to BarTender 12.1 or later.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00132 2nd percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by the CNA

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Total

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
Seagull Software, LLC.	BarTender 2021	R1 – 12.0.1	—	No fix listed	CNA

BarTender 2021 VendorSeagull Software, LLC. Affected R1 – 12.0.1 Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2026-25551
2026-10-03 Alias added: GHSA-g42f-xxvf-qj27

References

TI-2026-20658 Seagull Software BarTender Unauthenticated RCE via .NET Remoting Service CVSS 4.0CRITICAL 9.3

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences