CVE-2026-6103

Received Received - Intake

PharData Tar Header Size Parsing Integer Overflow

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: PHP Group

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-25

Last Modified

2026-09-25

Generated

2026-09-26

AI Q&A

2026-09-26

EPSS Evaluated

N/A

NVD

CVE-2026-6103

Affected Vendors & Products

Vendor	Product	Version / Range
php	php	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-190	The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Attack-Flow Graph

Executive Summary

This vulnerability involves a flaw in the phar_tar_number() function which parses the octal size field of a TAR header. The function converts this field into a uint32_t without checking for overflow. Since the field can hold values up to 0x1FFFFFFFF, values exceeding 0xFFFFFFFF wrap around silently. This causes the parser to skip an incorrect number of data blocks and treat attacker-controlled content as the next TAR header, allowing a crafted archive to inject false entries that PharData processes as valid.

Detection Guidance

This vulnerability involves a TAR header parsing issue in PHP's PharData. Detection requires checking for malformed TAR archives that exploit the octal size field overflow. Inspect PHP logs for PharData errors or unusual archive processing. Use tools like 'tar -tvf' to manually verify archive integrity. No direct network detection commands are available.

Impact Analysis

This vulnerability could allow an attacker to inject malicious entries into a TAR archive. When PharData processes the archive, it may extract these entries as legitimate files, potentially leading to unauthorized file creation or execution on the system. This could result in data corruption, unauthorized access, or further compromise of the affected system.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR or HIPAA by allowing unauthorized file content injection through crafted Phar archives. If exploited, it might lead to improper data handling or unauthorized access, which are key concerns under these regulations.

Mitigation Strategies

Update PHP to the latest patched version to address the phar_tar_number() overflow issue. Review and validate TAR archives before processing with PharData to prevent crafted entries from being interpreted as genuine files.

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