CVE-2017-12231
HighExploitedPublic exploitA vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
Published Sep 28, 2017 · Updated Apr 21, 2026
Key Facts
Patch immediately- CVE-2017-12231 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting IOS (Cisco).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 3, 2022. Public exploit code is available.
- EPSS estimates a 7.1% probability of exploitation in the next 30 days.
- Fixed versions are available, including IOS 15.6.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (30-day exploit likelihood)
7.1%
Higher than 94.1% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2017-12231 brief as a PDF
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Description
A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to the improper translation of H.323 messages that use the Registration, Admission, and Status (RAS) protocol and are sent to an affected device via IPv4 packets. An attacker could exploit this vulnerability by sending a crafted H.323 RAS packet through an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition. This vulnerability affects Cisco devices that are configured to use an application layer gateway with NAT (NAT ALG) for H.323 RAS messages. By default, a NAT ALG is enabled for H.323 RAS messages. Cisco Bug IDs: CSCvc57217.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Mar 3, 2022 | Mar 24, 2022 | Not reported |
| Industry KEV feed | Mar 3, 2022 | Mar 24, 2022 | Not reported |
| CIRCL KEV | Mar 3, 2022 | Mar 24, 2022 | Not reported |
| ENISA EUVD | Mar 3, 2022 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
2 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| IOSCisco | >= Cisco IOS | 15.6 |
Patched Releases
IOS
15.6
Timeline
Publicly disclosed
Sep 28, 2017
Added to CISA KEV
Mar 3, 2022
Added to Industry KEV feed
Mar 3, 2022
Added to CIRCL KEV
Mar 3, 2022
Added to ENISA EUVD
Mar 3, 2022
Last updated
Apr 21, 2026
Weakness Type
- CWE-399
References
- advisoryhttps://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-nat
- advisory101039
- advisory1039449
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
Affected: IOS (Cisco) versions >= Cisco IOS. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 3, 2022.
Yes. It was added on Mar 3, 2022 with a federal remediation due date of Mar 24, 2022.
Public exploit code is available.
Fixed versions are available, including IOS 15.6.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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