Medium
OOB write via unchecked multiplication
Type: advisorySources: OSV
In libcurl's base64 encode function, the output buffer is allocated as follows without any checks on `insize`: malloc( insize * 4 / 3 + 4 ) On systems with 32-bit addresses in userspace (e.g. x86, ARM, x32), the multiplication in the expression wraps around if `insize` is at least 1GB of data. If this happens, an undersized output buffer is allocated, but the full result is written, thus causing the memory behind the output buffer to be overwritten. If a username is set directly via `CURLOPT_USERNAME` (or curl's `-u, --user` option), this vulnerability can be triggered. The name has to be at least 512MB big in a 32-bit system. Systems with 64-bit versions of the `size_t` type are not affected by this issue.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2016-8617
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 09:37 UTC · Revision 1
Source evidence
In libcurl's base64 encode function, the output buffer is allocated as follows without any checks on `insize`: malloc( insize * 4 / 3 + 4 ) On systems with 32-bit addresses in userspace (e.g. x86, ARM, x32), the multiplication in the expression wraps around if `insize` is at least 1GB of data. If this happens, an undersized output buffer is allocated, but the full result is written, thus causing the memory behind the output buffer to be overwritten. If a username is set directly via `CURLOPT_USERNAME` (or curl's `-u, --user` option), this vulnerability can be triggered. The name has to be at least 512MB big in a 32-bit system. Systems with 64-bit versions of the `size_t` type are not affected by this issue.
osv:CURL-CVE-2016-8617
Complete source record
{
"id": "22e9edc07aa7686d2dad5a0dfe0fac911b1109b2cdf71d6174d4c23f0a3546c3",
"url": "https://osv.dev/vulnerability/CURL-CVE-2016-8617",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "OOB write via unchecked multiplication",
"summary": "In libcurl's base64 encode function, the output buffer is allocated as follows without any checks on `insize`: malloc( insize * 4 / 3 + 4 ) On systems with 32-bit addresses in userspace (e.g. x86, ARM, x32), the multiplication in the expression wraps around if `insize` is at least 1GB of data. If this happens, an undersized output buffer is allocated, but the full result is written, thus causing the memory behind the output buffer to be overwritten. If a username is set directly via `CURLOPT_USERNAME` (or curl's `-u, --user` option), this vulnerability can be triggered. The name has to be at least 512MB big in a 32-bit system. Systems with 64-bit versions of the `size_t` type are not affected by this issue.",
"evidence": "osv:CURL-CVE-2016-8617",
"products": [],
"severity": "medium",
"structured": {
"id": "CURL-CVE-2016-8617",
"aliases": [
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"source": "https://curl.se/docs/CURL-CVE-2016-8617.json",
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"target": {
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"vanir_signatures_modified": "2026-10-25T01:04:58Z"
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"modified": "2026-10-25T01:04:58.351914679Z",
"provider": "osv",
"references": [],
"provider_metadata": {
"CWE": {
"id": "CWE-131",
"desc": "Incorrect Calculation of Buffer Size"
},
"URL": "https://curl.se/docs/CVE-2016-8617.json",
"www": "https://curl.se/docs/CVE-2016-8617.html",
"affects": "both",
"package": "curl",
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"source_id": "core-osv",
"document_id": 444316,
"published_at": "2016-11-02T08:00:00+00:00"
}