IOS: Missing Release of Memory after Effective Lifetime
CVE-2026-20012 is a high-severity missing release of memory after effective lifetime vulnerability in IOS from Cisco, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected IOS versions: 15.2(1)S; 15.2(2)S; 15.2(1)S1, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.37% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of IOS you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | IOS | 15.2(1)S; 15.2(2)S; 15.2(1)S1; 15.2(4)S; 15.2(1)S2; 15.2(2)S1; 15.2(2)S2; 15.2(2)S0a; and 32 more ranges | Not stated |
| Cisco | Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.8.1; 9.8.1.5; 9.8.1.7; 9.8.2; 9.8.2.8; 9.8.2.14; 9.8.2.15; 9.8.2.17; and 32 more ranges | Not stated |
| Cisco | Cisco IOS XE Software | 3.5.0E; 3.5.1E; 3.5.2E; 3.5.3E; 3.11.1S; 3.11.2S; 3.11.0S; 3.11.3S; and 32 more ranges | Not stated |
| Cisco | Cisco Secure Firewall Threat Defense (FTD) Software | 6.2.3; 6.2.3.1; 6.2.3.2; 6.2.3.3; 6.2.3.4; 6.2.3.5; 6.2.3.6; 6.2.3.7; and 32 more ranges | Not stated |
| Cisco | Secure Firewall Threat Defense | 6.2.3; 6.2.3.1; 6.2.3.2; 6.2.3.3; 6.2.3.4; 6.2.3.5; 6.2.3.6; 6.2.3.7; and 32 more ranges | Not stated |
| Cisco | Adaptive Security Appliance Software | 9.8.1; 9.8.1.5; 9.8.1.7; 9.8.2; 9.8.2.8; 9.8.2.14; 9.8.2.15; 9.8.2.17; and 32 more ranges | Not stated |
| Cisco | iOS Xe | 3.5.0e; 3.5.1e; 3.5.2e; 3.5.3e; 3.6.0e; 3.6.1e; 3.6.2ae; 3.6.2e; and 32 more ranges | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. Scored by CNA (cisco.com).
Official description
A vulnerability in the Internet Key Exchange version 2 (IKEv2) feature of Cisco IOS Software, Cisco IOS XE Software, Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a memory leak, resulting in a denial of service (DoS) condition on an affected device. This vulnerability is due to improper parsing of IKEv2 packets. An attacker could exploit this vulnerability by sending crafted IKEv2 packets to an affected device. A successful exploit of Cisco IOS Software and IOS XE Software could allow the attacker to cause the affected device to reload, resulting in a DoS condition. A successful exploit of Cisco Secure Firewall ASA Software and Secure FTD Software could allow the attacker to partially exhaust system memory, resulting in system instability, such as the inability to establish new IKEv2 VPN sessions. A manual reboot of the device is required to recover from this condition.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Missing Release of Memory after Effective Lifetime
The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.
How developers prevent this class of flaw
- Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone. For example, glibc in Linux provides protection against free of invalid pointers. When using Xcode to target OS X or iOS, enable automatic reference counting (ARC). To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Consider using the Boehm-Demers-Weiser garbage collector (bdwgc), which can help avoid leaks.
More Missing Release of Memory after Effective Lifetime vulnerabilities (CWE-401)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in IOS
- 8.6 High severity
- 7.7 High severity
- 9.0 Critical severity
- 7.7 High severity
- 7.7 High severity
- 8.1 High severity
Recent Missing Release of Memory after Effective Lifetime vulnerabilities
- 7.5 High severity
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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