CVE-2023-20109Cisco IOS and IOS XE Group Encrypted Transport VPN Out-of-Bounds Write Vulnerability
CVE-2023-20109 is a out-of-bounds write in Cisco IOS and IOS XE, rated medium (6.6 on CVSS 3.1).
Why this priority: Exploited in the wild: listed in CISA's KEV catalog.
Published · Updated · NVD status: Analyzed
What it is
Code writes past the end of a buffer, corrupting memory in ways an attacker can often turn into code execution.
How it is reached
An attacker can exploit it over the network, with an administrator account, and nobody has to click anything. Success also depends on conditions the attacker does not fully control.
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 2023-10-10: it is being exploited in the wild. EPSS estimates a 2.5% chance of exploitation activity in the next 30 days, higher than 85% of scored CVEs.
What to do
- Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2023-10-31.
- No fixed version is listed yet. Find every place Cisco IOS and IOS XE runs, watch the references for a fix, and plan a replacement if it is no longer supported.
- While there is no fix, review who holds accounts that can reach it.
- Check exposed instances for signs of compromise, not only for the version.
Description from NVD
A vulnerability in the Cisco Group Encrypted Transport VPN (GET VPN) feature of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker who has administrative control of either a group member or a key server to execute arbitrary code on an affected device or cause the device to crash. This vulnerability is due to insufficient validation of attributes in the Group Domain of Interpretation (GDOI) and G-IKEv2 protocols of the GET VPN feature. An attacker could exploit this vulnerability by either compromising an installed key server or modifying the configuration of a group member to point to a key server that is controlled by the attacker. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a denial of service (DoS) condition. For more information, see the Details ["#details"] section of this advisory.
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 IOS and IOS XE 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?
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.