Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
A vulnerability in the Zone-Based Firewall (ZFW) component of Cisco IOS Software could allow an unauthenticated, remote attacker to cause an affected device to hang or reload.
The vulnerability is due to improper processing of specific HTTP packets when the device is configured for content filtering or HTTP application layer gateway inspection. An attacker could exploit this vulnerability by sending specific HTTP packets through an affected device. An exploit could allow the attacker to cause an affected device to hang or reload.
Cisco confirmed the vulnerability in a security advisory and released software updates.
Cisco devices that are running affected Cisco IOS Software versions are vulnerable when HTTP application layer gateway (ALG) inspection or Cisco IOS Content filtering is configured under the ZBFW.
Cisco has published a list of affected Cisco IOS Software releases in the security advisory. The "Vendor Announcements" section of this alert contains a link to the advisory.
To exploit this vulnerability, the attacker must send HTTP packets to the targeted system. To achieve this, the attacker may need access to trusted, internal network resources in which the targeted device may reside. This access requirement reduces the likelihood of a successful exploit.
Only transit traffic can trigger this vulnerability; HTTP traffic destined to a vulnerable device cannot trigger this vulnerability.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
An unauthenticated, remote attacker could exploit this vulnerability to cause an affected device to hang or reload, resulting in a denial of service (DoS) condition.
The vulnerability is due to improper processing of specific HTTP packets when an affected device is configured for content filtering or HTTP ALG inspection.
An unauthenticated, remote attacker could exploit this vulnerability by sending specific HTTP packets through an affected device. If successful, the attacker could cause an affected device to hang or reload, resulting in a DoS condition.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at email@example.com.
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