Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C Library version 2.34 to version 2.43 could, with a crafted response from the configured DNS server, result in a violation of the DNS specification that causes the application to treat a non-answer section of the DNS response as a valid answer.
{
"unresolved_ranges": [
{
"source": "AFFECTED_FIELD",
"extracted_events": [
{
"introduced": "2.34"
},
{
"last_affected": "2.43"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4437.json",
"cna_assigner": "glibc",
"cwe_ids": [
"CWE-125"
]
}{
"source": "CPE_RANGE",
"extracted_events": [
{
"introduced": "2.34"
},
{
"last_affected": "2.43"
}
],
"cpe": "cpe:2.3:a:gnu:glibc:*:*:*:*:*:*:*:*"
}