From 51eadb692a5123b9838e5a68ecace3ac579a3a45 Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Mon, 25 Sep 2017 20:16:50 +0100 Subject: [PATCH] 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. CVE: CVE-2017-14495 Upstream-Status: Backport Signed-off-by: Sona Sarmadi --- CHANGELOG | 12 ++++++++++++ src/edns0.c | 8 +++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/CHANGELOG b/CHANGELOG index 8fe00ed..9523329 100644 --- a/CHANGELOG +++ b/CHANGELOG @@ -70,6 +70,18 @@ version 2.78 Credit to Felix Wilhelm, Fermin J. Serna, Gabriel Campana and Kevin Hamacher of the Google Security Team for finding this. + + 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. + CVE-2017-14495 applies. + Credit to Felix Wilhelm, Fermin J. Serna, Gabriel Campana + and Kevin Hamacher of the Google Security Team for + finding this. version 2.77 diff --git a/src/edns0.c b/src/edns0.c index 95b74ee..89b2692 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 */ -- 1.7.10.4