Office Long Term Servicing Channel
CVE-2026-20957
HIGH
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
AnalysisAI
Arbitrary code execution in Microsoft Office Excel results from an integer underflow vulnerability in the Long Term Servicing Channel and Online Server editions, exploitable by local attackers with user interaction. This HIGH severity flaw (CVSS 7.8) grants full system compromise capabilities including code execution, data theft, and service disruption with no available patch.
Technical ContextAI
Classified as CWE-122 (Heap-based Buffer Overflow). Affects 365 Apps. Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
RemediationAI
Monitor vendor advisories for a patch.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Integer Overflow
View allShare
External POC / Exploit Code
Leaving vuln.today