What is 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.
The record classifies CVE-2026-6103 under weakness class CWE-190. Its CVSS v3 base vector states that the flaw requires local access to the host, needs no prior authentication, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 49 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 4.3 — MEDIUM
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 2.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-09-25
Is CVE-2026-6103 being exploited?
No public exploitation evidence for CVE-2026-6103 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-09-25. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.
Affected products and versions
- PHP Group: PHP
How to fix CVE-2026-6103
Vendor advisory: https://github.com/php/php-src/security/advisories/GHSA-j3wh-g957-2m85. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-6103
1 tracked threat in the Threadlinqs corpus references CVE-2026-6103, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, NVD. This product uses the NVD API but is not endorsed or certified by the NVD.