Cyber Resilience

CVE-2026-45034

CriticalRCE

Published: 22 June 2026

Published
22 June 2026
Modified
23 June 2026
KEV Added
Patch
CVSS Score v4 9.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0035 27.1th percentile
Risk Priority 70 floored blend · peak EPSS

Summary

CVE-2026-45034 is a critical-severity Deserialization of Untrusted Data (CWE-502) vulnerability. Its CVSS base score is 9.2 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 27.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability details

PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. Prior to 1.30.5, CVE-2026-34084 was patched by the helper File::prohibitWrappers. The helper calls parse_url($filename, PHP_URL_SCHEME) and then checks is_string($scheme) && strlen($scheme) > 1 to reject stream wrappers such…

more

as phar://, php://, data:// or expect://. The check is not equivalent to "does the path contain a wrapper". When the input has the form phar:///path/file.phar/inner with three or more slashes after the scheme, parse_url returns boolean false instead of returning the scheme string. The is_string($scheme) branch is therefore skipped, the helper returns without throwing, and the caller proceeds. PHP's stream layer, however, still treats phar:///... as a valid phar wrapper and opens the underlying phar file. The result is that IOFactory::load($attackerPath) walks past the patch and still touches the phar wrapper. On PHP 7.x, simply reaching the phar wrapper via is_file is enough for PHP to automatically deserialize the phar metadata, which in turn invokes the magic methods __wakeup and __destruct of an attacker controlled object and gives full RCE. On PHP 8.x, automatic metadata deserialization for plain file ops was removed, so the chain at the PhpSpreadsheet layer reduces to a phar wrapper file read primitive, and RCE only resurfaces if the downstream consumer ever calls Phar::getMetadata. This vulnerability is fixed in 1.30.5.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
Why these techniques?

Bypass of stream wrapper filter enables attacker-controlled PHAR deserialization via IOFactory::load on untrusted spreadsheet input, directly facilitating remote code execution against a public-facing PHP application.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

Affected Assets

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-502

Penetration testing supplies malicious serialized objects, detecting unsafe deserialization and supporting corrective actions.

addresses: CWE-502

Evaluation of untrusted data handling (deserialization testing) reveals unsafe processing, which the required remediation process addresses.

addresses: CWE-502

Untrusted serialized data can be deserialized and observed inside the chamber, blocking gadget-chain exploitation outside the sandbox.

addresses: CWE-502

Validates or rejects untrusted serialized data before deserialization occurs.

addresses: CWE-502

Identifies and blocks malicious code introduced through deserialization of untrusted data at system boundaries.

addresses: CWE-502

Integrity verification of serialized information can detect tampering before deserialization occurs.

addresses: CWE-502

Provenance of associated data allows detection of untrusted sources before deserialization or processing occurs.

References