CVE-2025-14177: PHP getimagesize() Info Disclosure Bug

CVE-2025-14177 Overview

CVE-2025-14177 is an uninitialized memory use vulnerability affecting multiple versions of PHP. The vulnerability exists in the getimagesize() function, which may leak uninitialized heap memory into APPn segments (e.g., APP1) when reading images in multi-chunk mode, such as via php://filter. This occurs due to a bug in php_read_stream_all_chunks() that overwrites the buffer without advancing the pointer, leaving tail bytes uninitialized. Successful exploitation may lead to information disclosure of sensitive heap data, compromising the confidentiality of the target server.

Critical Impact

Attackers can potentially extract sensitive heap data from PHP servers by exploiting the uninitialized memory leak in image processing functions, leading to information disclosure that could expose credentials, session tokens, or other confidential data stored in memory.

Affected Products

• PHP versions 8.1.* before 8.1.34
• PHP versions 8.2.* before 8.2.30
• PHP versions 8.3.* before 8.3.29
• PHP versions 8.4.* before 8.4.16
• PHP versions 8.5.* before 8.5.1

Discovery Timeline

• 2025-12-27 - CVE-2025-14177 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-14177

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), though it specifically manifests as an uninitialized heap memory disclosure issue. The root problem lies in the php_read_stream_all_chunks() function's buffer handling logic when processing image data in multi-chunk mode.

When PHP processes images through stream wrappers like php://filter, the getimagesize() function reads image data in chunks. The vulnerable code path incorrectly overwrites the buffer without properly advancing the write pointer, causing subsequent reads to include tail bytes that were never initialized with valid data. These uninitialized bytes contain whatever data previously resided in that heap memory location, potentially including sensitive information from prior operations.

The attack surface is network-accessible and requires no authentication, though exploitation complexity is elevated due to the need for specific conditions to trigger the vulnerable code path. The vulnerability affects only confidentiality, with no direct impact on integrity or availability.

Root Cause

The vulnerability stems from a logic error in php_read_stream_all_chunks() within the PHP source code. When reading image data in multi-chunk mode, the function overwrites the buffer contents but fails to advance the buffer pointer accordingly. This implementation flaw results in the tail portion of the buffer remaining uninitialized, containing stale heap data from previous memory allocations. When the APPn segment data is subsequently processed and returned, these uninitialized bytes are included in the output, leaking heap contents to the attacker.

Attack Vector

Exploitation of CVE-2025-14177 requires an attacker to cause a vulnerable PHP server to process a specially crafted image file through the getimagesize() function using multi-chunk reading mode. This can be achieved through:

1. Uploading a malicious image to a web application that processes images using getimagesize()
2. Triggering image processing through php://filter stream wrappers
3. Manipulating image metadata to force multi-chunk processing

The vulnerability exists when the server processes image files through stream wrappers in multi-chunk mode. The attacker crafts an image that triggers the vulnerable code path, causing uninitialized heap memory to be included in the APPn segment response data. The leaked memory contents could reveal sensitive information such as session identifiers, database credentials, encryption keys, or other confidential data that was previously stored in the same heap region.

For detailed technical information, see the PHP Security Advisory on GitHub.

Detection Methods for CVE-2025-14177

Indicators of Compromise

• Unusual patterns in image processing requests using php://filter stream wrappers
• Excessive calls to getimagesize() with non-standard stream inputs
• Unexpected data patterns in image metadata responses indicating memory leakage
• Log entries showing repeated image processing failures or anomalies

Detection Strategies

• Monitor PHP error logs for anomalies related to getimagesize() function calls
• Implement application-layer monitoring for suspicious use of php://filter in image processing contexts
• Deploy web application firewalls (WAF) with rules to detect attempts to exploit stream wrapper vulnerabilities
• Use SentinelOne Singularity platform to detect unusual memory access patterns in PHP processes

Monitoring Recommendations

• Enable verbose logging for PHP image processing functions to capture potential exploitation attempts
• Configure alerts for unusual patterns in APPn segment data sizes or content
• Monitor for reconnaissance activities targeting PHP version fingerprinting
• Implement file integrity monitoring on PHP configuration files to detect unauthorized changes

How to Mitigate CVE-2025-14177

Immediate Actions Required

• Update PHP to the patched versions: 8.1.34, 8.2.30, 8.3.29, 8.4.16, or 8.5.1 depending on your installed branch
• Audit applications for use of getimagesize() with stream wrappers, particularly php://filter
• Implement input validation to restrict image processing to trusted file sources
• Consider temporarily disabling or restricting stream wrapper usage in image processing until patches are applied

Patch Information

PHP has released security patches addressing this vulnerability across all affected version branches. Organizations should upgrade to the following minimum versions to remediate CVE-2025-14177:

For additional details, refer to the PHP Security Advisory.

Workarounds

• Restrict access to getimagesize() function through PHP disable_functions directive where not required
• Implement application-level filtering to prevent use of php://filter with image processing functions
• Use alternative image processing libraries that do not rely on the affected PHP functions
• Deploy network-level controls to limit exposure of vulnerable PHP applications

# PHP configuration hardening example (php.ini)
# Disable stream wrappers for image processing if not required
allow_url_fopen = Off

# Restrict dangerous functions if getimagesize() is not needed
# Note: Only disable if your application does not require these functions
disable_functions = getimagesize