Published Sep 25, 2026Sources checked Nov 13, 2026
3.3LOWCVSS out of 10
What this means
Review the available evidence
CVE-2026-6103 and is rated Low severity with a CVSS score of 3.3. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.
What to do next
Remediation and response
Microsoft Security Response Center guidance
Vendor revision: Oct 7, 2026
Release Notes
Vendor-listed releases
8.3.35-1
CISA KEVNot listedBased on the latest collected catalog
EPSS0.2%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2026-6103?
phar_tar_number() parses the octal size field of a TAR header into a uint32_t with no overflow check. The field is 11 octal digits wide and holds values up to 0x1FFFFFFFF, so a size above 0xFFFFFFFF silently wraps.
The parser then skips the wrong number of data blocks and interprets attacker-controlled file content as the next TAR header, which lets a crafted archive inject entries that PharData reports and extracts as if they were genuine.