From f2ad2cecb55825f7e4409222de1688b9ceebceda Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Mon, 25 Sep 2017 20:16:50 +0100 Subject: [PATCH 6/9] Security fix, CVE-2017-14495, OOM in DNS response creation. Fix out-of-memory Dos vulnerability. An attacker which can send malicious DNS queries to dnsmasq can trigger memory allocations in the add_pseudoheader function The allocated memory is never freed which leads to a DoS through memory exhaustion. dnsmasq is vulnerable only if one of the following option is specified: --add-mac, --add-cpe-id or --add-subnet. --- src/edns0.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/src/edns0.c b/src/edns0.c index eed135e..5bdc133 100644 --- a/src/edns0.c +++ b/src/edns0.c @@ -192,9 +192,15 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l !(p = skip_section(p, ntohs(header->ancount) + ntohs(header->nscount) + ntohs(header->arcount), header, plen))) + { + free(buff); return plen; + } if (p + 11 > limit) - return plen; /* Too big */ + { + free(buff); + return plen; /* Too big */ + } *p++ = 0; /* empty name */ PUTSHORT(T_OPT, p); PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */ -- 2.9.5