Integer overflow in PHP
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.
Vulnerability class: Integer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (5.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 5.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.000
Affected products
Weakness classification (CWE)
References
- github.com/php/php-src/security/advisories/GHSA-j3wh-g957-2m85 (Exploit, vendor-advisory, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-6103?
- CVE-2026-6103 is a medium-severity vulnerability in PHP, classified under Integer Overflow or Wraparound. CVSS score: 4.3/10. Published 2026-09-25.
- How severe is CVE-2026-6103?
- Medium severity. CVSS v3 base score is 4.3 out of 10.