Background exploitation KEV catalog

CVE-2023-20109

Cisco IOS and IOS XE Group Encrypted Transport VPN Out-of-Bounds Write Vulnerability

CheckOps priority index

3.9/10 Patch within 7 days

Severity6.6

Probability0.3

Exploitation2/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 2.5% higher than 84.7% of CVEs

CVSS 3.1 6.6 AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:

Exploited for 1,120 days 10 Oct 2023

CISA due date 31 Oct 2023 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 2 / 5

KEV catalog (CISA)10 Oct 2023
Exploited in EUVD (ENISA)10 Oct 2023
Used by ransomwareno
EPSS above 10 %2.5%
No account, over the networkno

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Description ENISA EUVD

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.

Affected products

IOSCisco IOS XE SoftwareIOS and IOS XE

Affected versions

15.3(1)S
12.4(24)MDB1
17.9.1w
15.5(3)M0a
15.8(3)M10
15.2(4)E
3.16.8S
17.1.1a
15.0(2)SE12
15.6(1)T
16.8.1d
17.8.1a

Weaknesses (CWE)

CWE-787

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

27 Sept 2023
Published
10 Oct 2023
Exploitation reported (ENISA)
10 Oct 2023
Added to the KEV catalog
31 Oct 2023
CISA remediation due date

References

Other exploited vulnerabilities from the same vendor

CVE-2026-76418Cisco Secure Firewall ASA Software and Cisco Secure FTD Software Unchecked Return Value to NULL Pointer Dereference Vulnerability
5.3 · Rising fast
CVE-2026-76519Cisco Secure Email Gateway Relative Path Traversal Vulnerability
5.8 · Rising fast
CVE-2026-76504Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability
7.5 · Actively exploited
CVE-2026-76460Cisco Identity Services Engine Incorrect Use of Privileged APIs Vulnerability
8.7 · Actively exploited
CVE-2026-76461Cisco Secure Email Gateway SQL Injection Vulnerability
7.2 · Actively exploited
CVE-2026-20079Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel Vulnerability
9.1 · Actively exploited