Critical
Security advisory
The bcpowmod function in ext/bcmath/bcmath.c in PHP before 5.5.35, 5.6.x before 5.6.21, and 7.x before 7.0.6 modifies certain data structures without considering whether they are copies of the _zero_, _one_, or _two_ global variable, which allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted call.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2016-4538
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 04:26 UTC · Revision 1
Source evidence
The bcpowmod function in ext/bcmath/bcmath.c in PHP before 5.5.35, 5.6.x before 5.6.21, and 7.x before 7.0.6 modifies certain data structures without considering whether they are copies of the _zero_, _one_, or _two_ global variable, which allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted call.
osv:CVE-2016-4538
Complete source record
{
"id": "169e9778e9a052a202e3c1747ffdd8077b38c02189d96e215dfe4710a11e4bc0",
"url": "https://osv.dev/vulnerability/CVE-2016-4538",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2016-4538",
"summary": "The bcpowmod function in ext/bcmath/bcmath.c in PHP before 5.5.35, 5.6.x before 5.6.21, and 7.x before 7.0.6 modifies certain data structures without considering whether they are copies of the _zero_, _one_, or _two_ global variable, which allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted call.",
"evidence": "osv:CVE-2016-4538",
"products": [],
"severity": "critical",
"structured": {
"id": "CVE-2016-4538",
"aliases": [
"CVE-2016-4538"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/php/php-src",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"last_affected": "8f0acd6a9022e01f5c438c395eb619f34f89567e"
},
{
"introduced": "fc1df8e7a6886e29a6ed5bef3f674ac61164e847"
},
{
"last_affected": "249a8fd9ae2324c84ede7ecfca6f6026e6d87df6"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:php:php:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"last_affected": "5.5.33"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.0:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.0"
},
{
"last_affected": "5.6.0"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.1:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.1"
},
{
"last_affected": "5.6.1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.2:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.2"
},
{
"last_affected": "5.6.2"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.3:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.3"
},
{
"last_affected": "5.6.3"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.4:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.4"
},
{
"last_affected": "5.6.4"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.5:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.5"
},
{
"last_affected": "5.6.5"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.6:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.6"
},
{
"last_affected": "5.6.6"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.7:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.7"
},
{
"last_affected": "5.6.7"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.8:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.8"
},
{
"last_affected": "5.6.8"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.9:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.9"
},
{
"last_affected": "5.6.9"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.10:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.10"
},
{
"last_affected": "5.6.10"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.11:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.11"
},
{
"last_affected": "5.6.11"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.12:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.12"
},
{
"last_affected": "5.6.12"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.13:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.13"
},
{
"last_affected": "5.6.13"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.14:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.14"
},
{
"last_affected": "5.6.14"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.15:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.15"
},
{
"last_affected": "5.6.15"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.16:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.16"
},
{
"last_affected": "5.6.16"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.17:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.17"
},
{
"last_affected": "5.6.17"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.18:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.18"
},
{
"last_affected": "5.6.18"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.19:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.19"
},
{
"last_affected": "5.6.19"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:5.6.20:*:*:*:*:*:*:*",
"range": [
{
"introduced": "5.6.20"
},
{
"last_affected": "5.6.20"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:7.0.0:*:*:*:*:*:*:*",
"range": [
{
"introduced": "7.0.0"
},
{
"last_affected": "7.0.0"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:7.0.1:*:*:*:*:*:*:*",
"range": [
{
"introduced": "7.0.1"
},
{
"last_affected": "7.0.1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:7.0.2:*:*:*:*:*:*:*",
"range": [
{
"introduced": "7.0.2"
},
{
"last_affected": "7.0.2"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:7.0.3:*:*:*:*:*:*:*",
"range": [
{
"introduced": "7.0.3"
},
{
"last_affected": "7.0.3"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:7.0.4:*:*:*:*:*:*:*",
"range": [
{
"introduced": "7.0.4"
},
{
"last_affected": "7.0.4"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:php:php:7.0.5:*:*:*:*:*:*:*",
"range": [
{
"introduced": "7.0.5"
},
{
"last_affected": "7.0.5"
}
],
"source": "CPE_STRING"
}
]
}
}
],
"versions": [
"5.6.0",
"5.6.1",
"5.6.10",
"5.6.11",
"5.6.12",
"5.6.13",
"5.6.14",
"5.6.15",
"5.6.16",
"5.6.17",
"5.6.18",
"5.6.19",
"5.6.2",
"5.6.20",
"5.6.3",
"5.6.4",
"5.6.5",
"5.6.6",
"5.6.7",
"5.6.8",
"5.6.9",
"7.0.0",
"7.0.1",
"7.0.2",
"7.0.3",
"7.0.4",
"7.0.5",
"php-7.0.5",
"php-7.0.5RC1",
"php-5.5.33",
"POST_PHP7_NSAPI_REMOVAL",
"PRE_PHP7_NSAPI_REMOVAL",
"PRE_PHP7_EREG_MYSQL_REMOVALS",
"PRE_PHP7_REMOVALS",
"POST_PHP7_REMOVALS",
"POST_AST_MERGE",
"PRE_AST_MERGE",
"POST_64BIT_BRANCH_MERGE",
"PRE_64BIT_BRANCH_MERGE",
"POST_PHPNG_MERGE"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2016-4538.json"
}
}
],
"modified": "2026-10-24T10:30:18.374281789Z",
"provider": "osv",
"references": [
"https://git.php.net/?p=php-src.git%3Ba=commit%3Bh=d650063a0457aec56364e4005a636dc6c401f9cd",
"https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05240731",
"https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05320149",
"https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05390722",
"https://security.gentoo.org/glsa/201611-22",
"https://bugs.php.net/bug.php?id=72093"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:o:fedoraproject:fedora:24:*:*:*:*:*:*:*"
],
"vendor_product": "fedoraproject:fedora",
"extracted_events": [
{
"range": [
{
"introduced": "24"
},
{
"last_affected": "24"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:o:opensuse:leap:42.1:*:*:*:*:*:*:*"
],
"vendor_product": "opensuse:leap",
"extracted_events": [
{
"range": [
{
"introduced": "42.1"
},
{
"last_affected": "42.1"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2016-4538",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 429758,
"published_at": "2016-05-22T01:59:22.933+00:00"
}