Cisco Reissues Patches for Critical Firewall Flaw

Cisco has reissued patches for a critical vulnerability affecting some of the company’s security appliances after identifying new attack vectors and additional affected features, and determining that the original fix had been incomplete.

The networking giant informed customers in late January that its Adaptive Security Appliance (ASA) software is affected by a serious flaw that can be exploited by a remote and unauthenticated attacker to execute arbitrary code or cause a denial-of-service (DoS) condition.

The vulnerability, tracked as CVE-2018-0101, affects several products running ASA software, including Firepower firewalls, 3000 series industrial security appliances, ASA 5000 and 5500 series appliances, 1000V cloud firewalls, ASA service modules for routers and switches, and Firepower Threat Defense (FTD) software.

The details of the security hole were disclosed on February 2 at a conference by Cedric Halbronn, an NCC Group researcher who reported the bug to Cisco.

“When exploited, this vulnerability known as CVE-2018-0101 allows the attacker to see all of the data passing through the system and provides them with administrative privileges, enabling them to remotely gain access to the network behind it,” NCC Group said in a blog post. “Targeting the vulnerability without a specially-crafted exploit would cause the firewall to crash and would potentially disrupt the connectivity to the network.”

Cisco initially told customers that the vulnerability is related to the webvpn feature, but further analysis revealed additional attack vectors and impacted features.

In an updated advisory published on Monday, the company said the flaw affects more than a dozen features, including Adaptive Security Device Manager (ASDM), AnyConnect IKEv2 Remote Access and SSL VPN, Cisco Security Manager, Clientless SSL VPN, Cut-Through Proxy, Local Certificate Authority, Mobile Device Manager Proxy, Mobile User Security, Proxy Bypass, the REST API, and Security Assertion Markup Language (SAML) Single Sign-on (SSO).

A specific configuration for each of these features introduces the vulnerability, but some of the configurations are reportedly common for the affected firewalls.

Cisco has now released a new set of patches after discovering that the initial fixes were vulnerable to additional DoS attacks.

“While Cisco PSIRT is not aware of any malicious use of this vulnerability, Cisco highly recommends all customers upgrade to a fixed software version,” said Omar Santos, principal engineer in the Cisco Product Security Incident Response Team (PSIRT). “This proactive patching is especially important for those customers whose devices and configurations include potential exposure through the expanded attack surface.”

Cato Networks reported that there are roughly 120,000 ASA devices with the webvpn feature enabled accessible from the Internet. Furthermore, some system administrators have complained about the availability of patches and the time it takes to apply them.

System admin Colin Edwards posted a blog post suggesting that Cisco may have started patching the vulnerability 80 days before publishing a security advisory to warn customers.

“I can understand some of the challenges that Cisco and their peers are up against. But even with that, I’m not sure that customers should be willing to accept that an advisory like this can be withheld for eighty days after some fixes are already available,” Edwards said. “Eighty days is a long time, and it’s a particularly long time for a vulnerability with a CVSS Score of 10 that affects devices that are usually directly connected to the internet.”

Santos said the company published the advisory shortly after learning that there had been public knowledge of the vulnerability.

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