The vulnerability exists in PHP's phar_tar_number() function, which parses the octal size field of a TAR header into a 32-bit unsigned integer without checking for overflow. The size field can hold values up to 0x1FFFFFFFF, but values above 0xFFFFFFFF cause silent wraparound. This causes the parser to skip an incorrect number of data blocks and interpret attacker-controlled file content as a subsequent TAR header. As a result, a crafted Phar archive can inject entries that the PharData component reports and extracts as if they were legitimate, potentially leading to integrity violations.

An attacker can craft a malicious Phar archive that exploits the integer overflow to inject unauthorized entries during archive extraction. This can lead to integrity issues where files extracted are not those intended by the archive creator. There is no direct impact on confidentiality or availability according to the CVSS vector. The attack requires local access (AV:L) and has low complexity (AC:L) with no privileges required (PR:N) and no user interaction (UI:N).

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Until a patch is available, avoid processing untrusted Phar archives or use alternative archive handling methods that do not rely on the vulnerable parsing function.