ID

VAR-200609-0146

CVE

CVE-2006-4650

TITLE

Cisco IOS Rogue GRE Vulnerability that bypasses packet access control

DESCRIPTION

Cisco IOS 12.0, 12.1, and 12.2, when GRE IP tunneling is used and the RFC2784 compliance fixes are missing, does not verify the offset field of a GRE packet during decapsulation, which leads to an integer overflow that references data from incorrect memory locations, which allows remote attackers to inject crafted packets into the routing queue, possibly bypassing intended router ACLs. Cisco IOS Contains source routing information GRE Packet Offset A vulnerability exists where the starting position of the source routing information is not properly calculated when releasing an encapsulated packet due to improper checks on the field.Inappropriate areas of the packet may be referred to as source routing information, and packets released from the device may be forwarded. Cisco IOS is prone to multiple vulnerabilities when decapsulating GRE routing packets. Specifically, these issues present themselves when the device handles malicious GRE packets with oversized header offset values, and also with malicious GRE packets containing modified source-routing data. A successful attack can allow an attacker to disclose sensitive information in process memory buffers, bypass security restrictions, deny service to legitimate users, or possibly crash the Cisco IOS operating system. Cisco IOS 12.0, 12.1, and 12.2 based trains are reported vulnerable. All devices running affected versions of Cisco IOS that are configured with GRE IP or GRE IP multipoint tunnels are vulnerable to this issue. Remote attackers may cause errors in device processing packets. If a specially crafted GRE message is received, the IOS device does not verify whether the offset field points to the message. If the offset value is set to a negative value, the IOS directly subtracts the offset from the integer containing the full length of the IP message. shift, resulting in buffer access out-of-bounds overflow. This may lead to interpreting the rest of the memory contents of the ring buffer as payload IP packets and re-injecting them into the routing queue with large length information: GRE decapsulated IP 0.3.74.0->0.0.1.30 (len =65407, ttl=39) GRE decapsulated IP 176.94.8.0- > 0.0.0.0 (len=64904, ttl=0) GRE decapsulated IP 0.15.31.193- > 176.94.8.0 (len=64894, ttl=237) GRE decapsulated IP 128.42.131.220->128.0.3.74 (len=64884, ttl=128) If the ring buffer can be carefully filled with legitimate traffic containing IP headers at the appropriate offsets, an attacker can create many An IP packet with a large length value. ---------------------------------------------------------------------- Want to work within IT-Security? Secunia is expanding its team of highly skilled security experts. We will help with relocation and obtaining a work permit. Currently the following type of positions are available: http://secunia.com/quality_assurance_analyst/ http://secunia.com/web_application_security_specialist/ http://secunia.com/hardcore_disassembler_and_reverse_engineer/ ---------------------------------------------------------------------- TITLE: Cisco IOS GRE Decapsulation Vulnerability SECUNIA ADVISORY ID: SA21783 VERIFY ADVISORY: http://secunia.com/advisories/21783/ CRITICAL: Less critical IMPACT: Security Bypass WHERE: >From local network OPERATING SYSTEM: Cisco IOS R12.x http://secunia.com/product/50/ Cisco IOS 12.x http://secunia.com/product/182/ DESCRIPTION: FX has reported a vulnerability in Cisco IOS, which can be exploited by malicious people to bypass certain security restrictions. This can potentially be exploited to bypass access control lists on the router by sending specially crafted packets. NOTE: Cisco IOS version 12.0S, with a revision later than 12.0(23)S, with CEF enabled is not affected. SOLUTION: Apply patch CSCuk27655, CSCea22552, or CSCei62762. PROVIDED AND/OR DISCOVERED BY: FX, Phenoelit. ORIGINAL ADVISORY: Phenoelit: http://www.phenoelit.de/stuff/CiscoGRE.txt Cisco: http://www.cisco.com/warp/public/707/cisco-sr-20060906-gre.shtml ---------------------------------------------------------------------- About: This Advisory was delivered by Secunia as a free service to help everybody keeping their systems up to date against the latest vulnerabilities. Subscribe: http://secunia.com/secunia_security_advisories/ Definitions: (Criticality, Where etc.) http://secunia.com/about_secunia_advisories/ Please Note: Secunia recommends that you verify all advisories you receive by clicking the link. Secunia NEVER sends attached files with advisories. Secunia does not advise people to install third party patches, only use those supplied by the vendor. ---------------------------------------------------------------------- Unsubscribe: Secunia Security Advisories http://secunia.com/sec_adv_unsubscribe/?email=packet%40packetstormsecurity.org ----------------------------------------------------------------------

AFFECTED PRODUCTS