CVE-2023-20109: Cisco IOS and IOS XE

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run Cisco IOS and IOS XE. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2023-10-10, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2023-10-31; treat that as the outer limit, not the target.
EPSS 2.5%, percentile 84: FIRST’s model estimates a 2.5% chance of exploitation activity in the next 30 days, higher than 84% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
Needs an account (high (admin)). Exposure depends on who can log in.

What it is

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.

CISA’s summary

Cisco IOS and IOS XE contain an out-of-bounds write vulnerability in the Group Encrypted Transport VPN (GET VPN) feature that could allow an authenticated, remote attacker who has administrative control of either a group member or a key server to execute malicious code or cause a device to crash.

Weakness type: CWE-787.

Product: Cisco IOS and IOS XE · Assigned by: cisco · Published: 2023-09-27

Affected and fixed versions

Vendor	Product	Affected versions (per CVE record)
Cisco	IOS	12.4(24)T, 12.4(24)T3, 12.4(22)T1, 12.4(24)T5, 12.4(24)T4, 12.4(22)T, 12.4(24)T8, 12.4(24)T2, 12.4(22)T5, 12.4(22)T4, 12.4(24)T1, 12.4(24)T7
Cisco	Cisco IOS XE Software	3.7.0S, 3.7.1S, 3.7.2S, 3.7.3S, 3.7.4S, 3.7.5S, 3.7.6S, 3.7.7S, 3.7.4aS, 3.7.2tS, 3.7.0bS, 3.7.1aS

Severity scores

Scored by	CVSS	Score	Vector
cisco	3.1	6.6 Medium	`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H`

Attack vector: network (remotely reachable)
Attack complexity: high (needs special conditions)
Privileges required: high (admin)
User interaction: none
Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: added 2023-10-10; federal due date 2023-10-31. Known ransomware use: Unknown.
CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
CISA SSVC assessment: exploitation active, automatable no, technical impact total.
FIRST EPSS (model of 2026-10-21): 2.48% probability of exploitation activity in the next 30 days; percentile 84.

Timeline

2023-09-27 — CVE record published by cisco
2023-10-10 — Added to CISA’s Known Exploited Vulnerabilities catalog
2023-10-31 — CISA remediation deadline for US federal agencies
2025-10-21 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.