CVE-2021-1620
No exploitation reported by the sources we read.
- Published2021-09-23
- WeaknessCWE-563 · CWE-772
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
A vulnerability in the Internet Key Exchange Version 2 (IKEv2) support for the AutoReconnect feature of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to exhaust the free IP addresses from the assigned local pool. This vulnerability occurs because the code does not release the allocated IP address under certain failure conditions. An attacker could exploit this vulnerability by trying to connect to the device with a non-AnyConnect client. A successful exploit could allow the attacker to exhaust the IP addresses from the assigned local pool, which prevents users from logging in and leads to a denial of service (DoS) condition.
Timeline
dates in UTC- 2021-09-2303:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-1620?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-1620?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 15.1 | = 15.1\(3\)svt1 | no fix published | NVD |
| 15.1 | = 15.1\(3\)svt2 | no fix published | NVD |
| 15.1 | = 15.1\(3\)svu1 | no fix published | NVD |
| 12.2 | = 12.2\(6\)i1 | no fix published | NVD |
| 15.1 | = 15.1\(3\)svr1 | no fix published | NVD |
| 15.1 | = 15.1\(3\)svr2 | no fix published | NVD |
| 15.1 | = 15.1\(3\)svr3 | no fix published | NVD |
| 15.1 | = 15.1\(3\)svs | no fix published | NVD |
| 15.1 | = 15.1\(3\)svs1 | no fix published | NVD |
| 15.2 | = 15.2\(1\)sy2 | no fix published | NVD |
| 15.2 | = 15.2\(1\)sy3 | no fix published | NVD |
| 15.2 | = 15.2\(1\)sy4 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.8 | = 3.8.0e | no fix published | NVD |
| 3.8 | = 3.8.1e | no fix published | NVD |
| 3.8 | = 3.8.2e | no fix published | NVD |
| 3.8 | = 3.8.3e | no fix published | NVD |
| 3.8 | = 3.8.4e | no fix published | NVD |
| 3.8 | = 3.8.5ae | no fix published | NVD |
| 3.8 | = 3.8.5e | no fix published | NVD |
| 3.8 | = 3.8.6e | no fix published | NVD |
| 3.8 | = 3.8.7e | no fix published | NVD |
| 3.8 | = 3.8.8e | no fix published | NVD |
| 3.8 | = 3.8.9e | no fix published | NVD |
| 3.8 | = 3.8.10e | no fix published | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
Advisories and patches
- tools.cisco.comPatch · Vendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- Published
- 2021-09-23
- Last Modified
- 2026-06-17
- NVD status
- Analyzed
Frequently asked questions
What is CVE-2021-1620?
Is CVE-2021-1620 actively exploited?
What is the CVSS score for CVE-2021-1620?
Hear about the next vulnerability in your software
Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
No credit card required · No monthly cap on website lookups · 250 API requests/month
Go further
- Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
- Running this software? Vulnerability monitoring alerts you to new vulnerabilities in your products.
Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.