CVE-2026-6103: Phar TAR phar_tar_number() Integer Overflow - Archive Entry Injection

Severity: low (CVSS 3.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-09-25 · updated 2026-10-23
Weakness: CWE-190

Description

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.

Affected products

PHP: from 8.2.0 before 8.2.34; from 8.3.0 before 8.3.35; from 8.4.0 before 8.4.26; from 8.5.0 before 8.5.11 — fixed in 8.2.34, 8.3.35, 8.4.26, 8.5.11

How to fix

Upgrade to a fixed version: PHP 8.2.34, 8.3.35, 8.4.26, 8.5.11. Check the vendor advisory for mitigations.

References

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