# CVE-2026-6103 — PHP

> As of 2026-09-25, CVE-2026-6103 is a MEDIUM-severity vulnerability in PHP, CVSS v3.1 4.3. Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-6103, most recently “Multiple PHP Vulnerabilities Enable Denial of Service, TLS Verification Bypass, and Credential Leakage (CVE-2026-91765, CVE-2026-91768, CVE-2026-6103 and 8 Others) — GovCERT.HK A26-09-40”.

**Last updated:** 2026-09-25

## 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](https://cwe.mitre.org/data/definitions/190.html). 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 1 day 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

No vendor patch reference has been recorded for CVE-2026-6103 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## 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.

- [Multiple PHP Vulnerabilities Enable Denial of Service, TLS Verification Bypass, and Credential Leakage (CVE-2026-91765, CVE-2026-91768, CVE-2026-6103 and 8 Others) — GovCERT.HK A26-09-40](https://intel.threadlinqs.com/threat/TL-2026-2658) — MEDIUM · 2026-09-25

## Sources

Enriched from CVE.org, NVD. Last verified by Threadlinqs on 2026-09-26. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/php/php-src/security/advisories/GHSA-j3wh-g957-2m85)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-6103
Full detection coverage and IOCs for threats exploiting CVE-2026-6103 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp