NTLM buffer overflow via integer overflow
libcurl contains a buffer overrun flaw in the NTLM authentication code. The internal function `Curl_ntlm_core_mk_ntlmv2_hash` sums up the lengths of the username + password (= SUM) and multiplies the sum by two (= SIZE) to figure out how large storage to allocate from the heap. The SUM value is subsequently used to iterate over the input and generate output into the storage buffer. On systems with a 32-bit `size_t`, the math to calculate SIZE triggers an integer overflow when the combined lengths of the username and password is larger than 2GB (2^31 bytes). This integer overflow usually causes a tiny buffer to actually get allocated instead of the intended huge one, making the use of that buffer end up in a buffer overrun.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2017-8816
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 09:37 UTC · Revision 1
Source evidence
libcurl contains a buffer overrun flaw in the NTLM authentication code. The internal function `Curl_ntlm_core_mk_ntlmv2_hash` sums up the lengths of the username + password (= SUM) and multiplies the sum by two (= SIZE) to figure out how large storage to allocate from the heap. The SUM value is subsequently used to iterate over the input and generate output into the storage buffer. On systems with a 32-bit `size_t`, the math to calculate SIZE triggers an integer overflow when the combined lengths of the username and password is larger than 2GB (2^31 bytes). This integer overflow usually causes a tiny buffer to actually get allocated instead of the intended huge one, making the use of that buffer end up in a buffer overrun.
osv:CURL-CVE-2017-8816
Complete source record
{
"id": "b1db4dfc584ff07d12cdae32485368768e1355f24f165d3b1e7709ec955a45a1",
"url": "https://osv.dev/vulnerability/CURL-CVE-2017-8816",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "NTLM buffer overflow via integer overflow",
"summary": "libcurl contains a buffer overrun flaw in the NTLM authentication code. The internal function `Curl_ntlm_core_mk_ntlmv2_hash` sums up the lengths of the username + password (= SUM) and multiplies the sum by two (= SIZE) to figure out how large storage to allocate from the heap. The SUM value is subsequently used to iterate over the input and generate output into the storage buffer. On systems with a 32-bit `size_t`, the math to calculate SIZE triggers an integer overflow when the combined lengths of the username and password is larger than 2GB (2^31 bytes). This integer overflow usually causes a tiny buffer to actually get allocated instead of the intended huge one, making the use of that buffer end up in a buffer overrun.",
"evidence": "osv:CURL-CVE-2017-8816",
"products": [],
"severity": "medium",
"structured": {
"id": "CURL-CVE-2017-8816",
"aliases": [
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"CVE-2017-8816"
],
"affected": [
{
"ranges": [
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"type": "SEMVER",
"events": [
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"curl-7_41_0",
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],
"database_specific": {
"source": "https://curl.se/docs/CURL-CVE-2017-8816.json",
"vanir_signatures": [
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"source": "https://github.com/curl/curl.git/commit/7f2a1df6f5fc598750b2c6f34465c8d924db28cc",
"target": {
"file": "lib/curl_ntlm_core.c"
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"signature_type": "Line",
"signature_version": "v1"
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{
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"digest": {
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"source": "https://github.com/curl/curl.git/commit/7f2a1df6f5fc598750b2c6f34465c8d924db28cc",
"target": {
"file": "lib/curl_ntlm_core.c",
"function": "Curl_ntlm_core_mk_ntlmv2_hash"
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"signature_type": "Function",
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"vanir_signatures_modified": "2026-10-25T01:04:50Z"
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],
"modified": "2026-10-25T01:04:50.869689110Z",
"provider": "osv",
"references": [],
"provider_metadata": {
"CWE": {
"id": "CWE-131",
"desc": "Incorrect Calculation of Buffer Size"
},
"URL": "https://curl.se/docs/CVE-2017-8816.json",
"www": "https://curl.se/docs/CVE-2017-8816.html",
"affects": "both",
"package": "curl",
"severity": "Medium",
"last_affected": "7.56.1"
}
},
"related_cves": [
{
"value": "CVE-2017-8816",
"evidence": "/aliases"
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],
"security_relevant": true,
"severity_evidence": "/database_specific/severity"
},
"source_id": "core-osv",
"document_id": 444299,
"published_at": "2017-11-29T08:00:00+00:00"
}