CVE-2026-48062: CodeIgniter4 has a validation bypass when uploading file extensions via `ext_in` rule

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.8%, percentile 55: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 55% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes codeigniter4/framework (Composer (PHP)) < 4.7.2, fixed in 4.7.3. Check your lockfile, including transitive dependencies.

What it is

CodeIgniter is a PHP full-stack web framework. Prior to 4.7.3, the extin upload validation rule in system/Validation/StrictRules/FileRules.php checked the MIME-derived guessed extension instead of the client-provided filename extension. As a result, an uploaded file named shell.php containing GIF-like content could pass validation such as uploaded[avatar]|isimage[avatar]|mimein[avatar,image/gif]|extin[avatar,gif] because the detected MIME type maps to gif, even though the uploaded filename extension is php. Applications are impacted if they accept user-controlled uploads, rely on extin to validate the uploaded filename extension, save uploaded files using the original client filename with $file->move($path), store uploads in a web-accessible directory, and allow PHP or other executable files to run from that directory. In those conditions, this may lead to arbitrary code execution. This issue is fixed in version 4.7.3.

From the GitHub advisory

Impact The extin upload validation rule checked the MIME-derived guessed extension instead of the client-provided filename extension. As a result, an uploaded file named shell.php containing GIF-like content could pass validation such as:

because the detected MIME type maps to gif, even though the uploaded filename extension is php.

Applications are impacted if they: - accept user-controlled uploads, - rely on extin to validate the uploaded filename extension, - save uploaded files using the original client filename: $file->move($path), - store uploads in a web-accessible directory, - and allow PHP or other executable files to run from that directory.

In those conditions, this may lead to arbitrary code execution. The default application does not expose such an upload endpoint.

Patches Upgrade to v4.7.3 or later.

Weakness type: CWE-434.

Product: codeigniter4/framework (Composer (PHP)) · Assigned by: GitHub_M · Published: 2026-07-17

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.78% probability of exploitation activity in the next 30 days; percentile 55.

Timeline

• 2026-06-11 — GitHub-reviewed advisory GHSA-2gr4-ppc7-7mhx published (critical)
• 2026-07-17 — CVE record published by GitHub_M
• 2026-07-20 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-2gr4-ppc7-7mhx github.com
2. CVE.org record CVE-2026-48062 cve.org
3. NVD entry CVE-2026-48062 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. codeigniter.com codeigniter.com
5. codeigniter.com codeigniter.com
6. github.com github.com

Critical Composer (PHP) advisories · Today’s Security Digest