CVE-2018-0239 [High] | Input Validation Bypass in Staros

A vulnerability in the egress packet processing functionality of the Cisco StarOS operating system for Cisco Aggregation Services Router (ASR) 5700 Series devices and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to cause an interface on the device to cease forwarding packets. The device may need to be manually reloaded to clear this Interface Forwarding Denial of Service condition. The vulnerability is due to the failure to properly check that the length of a packet to transmit does not exceed the maximum supported length of the network interface card (NIC). An attacker could exploit this vulnerability by sending a crafted IP packet or a series of crafted IP fragments through an interface on the targeted device. A successful exploit could allow the attacker to cause the network interface to cease forwarding packets. This vulnerability could be triggered by either IPv4 or IPv6 network traffic. This vulnerability affects the following Cisco products when they are running the StarOS operating system and a virtual interface card is installed on the device: Aggregation Services Router (ASR) 5700 Series, Virtualized Packet Core-Distributed Instance (VPC-DI) System Software, Virtualized Packet Core-Single Instance (VPC-SI) System Software. Cisco Bug IDs: CSCvf32385.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-09	2.70%	3.26%	+0.55%
2	2025-07-17	3.20%	2.70%	-0.50%
3	2025-05-07	—	3.20%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-09

2.70%

3.26%

+0.55%

2025-07-17

3.20%

2.70%

-0.50%

2025-05-07

—

3.20%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:N/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:P) Partial availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:P): Partial availability impact.

10.0

2.9

[email protected]

Affected software / configurations for CVE-2018-0239

Vendor	Product	Version	Raw CPE
cisco	staros	21.0.v0.65819	cpe:2.3:o:cisco:staros:21.0.v0.65819:::::::*
cisco	staros	21.0.v4	cpe:2.3:o:cisco:staros:21.0.v4:::::::*
cisco	staros	21.1.v6	cpe:2.3:o:cisco:staros:21.1.v6:::::::*
cisco	staros	21.3.1	cpe:2.3:o:cisco:staros:21.3.1:::::::*
cisco	staros	21.4.0	cpe:2.3:o:cisco:staros:21.4.0:::::::*

References for CVE-2018-0239

URL	Tags
http://www.securityfocus.com/bid/103923	Third Party Advisory VDB Entry
http://www.securitytracker.com/id/1040720	Third Party Advisory VDB Entry
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180418-staros	Vendor Advisory

URL

CVE-2018-0239

Exploit prediction scoring system (EPSS) score for CVE-2018-0239

Common vulnerability scoring system (CVSS) metrics for CVE-2018-0239

Weakness enumeration for CVE-2018-0239

Affected software / configurations for CVE-2018-0239

References for CVE-2018-0239