CVE-2020-3556

CVE-2020-3556 is a high-severity vulnerability in Cisco Anyconnect Secure Mobility Client with a CVSS 3.x base score of 7.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Description

A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client Software could allow an authenticated, local attacker to cause a targeted AnyConnect user to execute a malicious script. The vulnerability is due to a lack of authentication to the IPC listener. An attacker could exploit this vulnerability by sending crafted IPC messages to the AnyConnect client IPC listener. A successful exploit could allow an attacker to cause the targeted AnyConnect user to execute a script. This script would execute with the privileges of the targeted AnyConnect user. In order to successfully exploit this vulnerability, there must be an ongoing AnyConnect session by the targeted user at the time of the attack. To exploit this vulnerability, the attacker would also need valid user credentials on the system upon which the AnyConnect client is being run. Cisco has not released software updates that address this vulnerability.

Frequently asked questions

What is CVE-2020-3556?
A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client Software could allow an authenticated, local attacker to cause a targeted AnyConnect user to execute a malicious script. The vulnerability is due to a lack of authentication to the IPC listener. An attacker could exploit this vulnerability by sending crafted IPC messages to the AnyConnect client IPC listener. A successful exploit could allow an attacker to cause the targeted AnyConnect user to execute a script. This script would execute with the privileges of the targeted AnyConnect user. In order to successfully exploit this vulnerability, there must be an ongoing AnyConnect session by the targeted user at the time of the attack. To exploit this vulnerability, the attacker would also need valid user credentials on the system upon which the AnyConnect client is being run. Cisco has not released software updates that address this vulnerability.
How severe is CVE-2020-3556?
CVE-2020-3556 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-3556 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-3556?
CVE-2020-3556 primarily affects Cisco Anyconnect Secure Mobility Client. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-3556?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-3556 published?
CVE-2020-3556 was published on 2020-11-06 and last updated on 2026-06-17.

References

Affected products (2)

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