From 073082ddc0aba7b8efa15a688d6183463b65effa Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Mon, 30 Mar 2026 16:24:33 +0100 Subject: [PATCH] Fix buffer overflow vulnerability in extract_addresses() CVE-2026-5172 Thanks to Hugo Martinez Ray for spotting this. The value of rdlen for an RR can be a lie, allowing the call to extract_name() at rfc1025.c:952 to advance the value of p1 past the calculated end of the record. The makes the calculation of bytes remaining in the RR underflow to a huge number and results in a massive heap OOB read and certain crash. --- src/rfc1035.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/rfc1035.c b/src/rfc1035.c index 792bb40..0afd0d3 100644 --- a/src/rfc1035.c +++ b/src/rfc1035.c @@ -953,7 +953,8 @@ int extract_addresses(struct dns_header *header, size_t qlen, char *name, time_t /* Name, extract it then re-encode. */ int len; - if (!extract_name(header, qlen, &p1, name, EXTR_NAME_EXTRACT, 0)) + /* rdlen may lie, and extract_name() advances p1 past where it says the record ends. */ + if (!extract_name(header, qlen, &p1, name, EXTR_NAME_EXTRACT, 0) || (p1 > endrr)) { blockdata_free(addr.rrblock.rrdata); return 2;