# Cisco IOS and IOS XE: Group Encrypted Transport VPN Out-of-Bounds Write (CVE-2023-20109) · pwn.watch

> 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. Added to CISA KEV on 2023-10-10.

Page: https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109 · generated 2026-10-22T22:00:08.805Z

## Status
- Severity: medium · status: closed · patch: patched
- Product: Cisco IOS and IOS XE
- Started: 2023-10-10 · closed: 2023-10-10
- CVEs: CVE-2023-20109
- Affected: See vendor advisory / CISA notes (versions not always listed in KEV feed)
- Fixed in: See vendor advisory linked in sources

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109/feed.xml
- JSON Feed: https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109.json
- This file: https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109/llms.txt

## Updates (newest first)
- 2023-10-10: CISA added CVE-2023-20109 to the KEV catalog (due 2023-10-31).

## Fix brief
# Security brief: Cisco IOS and IOS XE: Group Encrypted Transport VPN Out-of-Bounds Write (CVE-2023-20109)

Source: https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109 · status: closed (closed Oct 10, 2023) · severity: medium · updated Oct 10, 2023

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
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. Added to CISA KEV on 2023-10-10.

Severity detail: CVSS 6.6 (NVD), actively exploited (CISA KEV)

- Product: Cisco IOS and IOS XE
- CVE / advisory ids: CVE-2023-20109

## Affected versions
- See vendor advisory / CISA notes (versions not always listed in KEV feed)

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- See vendor advisory linked in sources

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Oct 10, 2023: CISA added CVE-2023-20109 to the KEV catalog (due 2023-10-31).

## Advisories
- [Vendor advisory: Cisco IOS and IOS XE](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-getvpn-rce-g8qR68sx) (Cisco)
- [NVD: CVE-2023-20109](https://nvd.nist.gov/vuln/detail/CVE-2023-20109) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Caveats
Derived from CISA KEV JSON feed catalogVersion 2026.10.21. Exact affected/fixed version strings are not always in the KEV record — verify against the vendor advisory URL. startedAt uses dateAdded (exploitation may have begun earlier).

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Machine-readable: https://pwn.watch/i/cisco-ios-and-ios-xe-cve-2023-20109.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.