CVE-2016-6366Cisco Adaptive Security Appliance (ASA) SNMP Buffer Overflow Vulnerability

Patch nowHigh8.8ExploitedEPSS 88%

CVE-2016-6366 is a classic buffer overflow in Cisco Adaptive Security Appliance (ASA), rated high (8.8 on CVSS 3.1).

Why this priority: Exploited in the wild: listed in CISA's KEV catalog.

Published 18 Aug 2016 · Updated 17 Jun 2026 · NVD status: Analyzed

What it is

Data is copied into a buffer without checking its size and overwrites what follows.

How it is reached

An attacker can exploit it over the network, with an ordinary user account, and nobody has to click anything.

What an attacker gains

A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker crash the process, read memory, or in the worst case run code.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2022-05-24: it is being exploited in the wild. EPSS estimates a 88% chance of exploitation activity in the next 30 days, higher than 100% of scored CVEs.

What to do

Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2022-06-14.
No fixed version is listed for Cisco Adaptive Security Appliance (ASA) itself; fixed versions for the other affected products are listed on this page.
Until it is patched, review who holds accounts that can reach it.
Check exposed instances for signs of compromise, not only for the version.

Description from NVD

Buffer overflow in Cisco Adaptive Security Appliance (ASA) Software through 9.4.2.3 on ASA 5500, ASA 5500-X, ASA Services Module, ASA 1000V, ASAv, Firepower 9300 ASA Security Module, PIX, and FWSM devices allows remote authenticated users to execute arbitrary code via crafted IPv4 SNMP packets, aka Bug ID CSCva92151 or EXTRABACON.

What this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

Network edge devices: VPNs, firewalls, routers and gateways. They sit between the internet and internal networks, so a flaw in one is often the first step into everything behind it.
Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
Native code: operating systems, browsers and firmware. The flaw sits wherever native code reads untrusted data.
Network appliances and media or file parsers. The flaw sits wherever native code reads untrusted data.

Trust boundaries in play

Authenticated network access. An account is needed, so exposure follows who can sign in: customers, partners or staff.
Wherever native code reads untrusted data. An attacker who crosses it can crash the process, read memory, or in the worst case run code.

Questions to answer about your own systems

Where does Cisco Adaptive Security Appliance (ASA) run in your systems, and at which version?
Which of those instances can be reached from the internet or partner networks?
What can it reach once compromised: which data stores, secrets and services?

See how Veriom maps an architecture Take the interactive tour

Advisories

Exploits and proofs of concept

Sources

CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.