CVE-2025-20239VulnerabilityPublished 14 Aug 2025

CVE-2025-20239: Cisco IOS · Memory Leak

Affects Cisco IOSSource CVE Database V5

Not known to be exploited · CVSS 8.6 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

8.6High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

1. Immediate deployment of Cisco's security patches or updates for all affected IOS, IOS XE, ASA, and FTD versions once available is critical. Organizations should prioritize patching devices exposed to untrusted networks. 2. Implement network-level filtering to restrict inbound IKEv2 traffic to trusted sources only, minimizing exposure to crafted packets from unauthorized attackers. 3. Monitor network traffic for unusual or malformed IKEv2 packets that could indicate exploitation attempts. 4. Employ rate limiting on VPN gateways to reduce the impact of potential memory exhaustion attacks. 5. Maintain up-to-date backups and have incident response plans ready for rapid recovery including manual reboot procedures. 6. Consider deploying redundant VPN gateways or failover mechanisms to maintain connectivity during an attack or device reboot. 7. Conduct thorough inventory and version audits of Cisco devices to identify vulnerable systems and prioritize remediation. 8. Use Cisco’s recommended configuration best practices for IKEv2 and VPN services to reduce attack surface. 9. Engage with Cisco support and security advisories regularly to stay informed about patches and mitigation updates. These steps go beyond generic advice by emphasizing network filtering, monitoring, redundancy, and operational readiness specific to this vulnerability’s characteristics.

Description

A vulnerability in the Internet Key Exchange Version 2 (IKEv2) feature of Cisco IOS Software, IOS XE Software, Secure Firewall Adaptive Security Appliance (ASA) Software, and 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. This vulnerability is due to a lack of proper processing of IKEv2 packets. An attacker could exploit this vulnerability by sending crafted IKEv2 packets to an affected device. In the case of Cisco IOS and IOS XE Software, a successful exploit could allow the attacker to cause the device to reload unexpectedly. In the case of Cisco ASA and FTD Software, a successful exploit could allow the attacker to partially exhaust system memory, causing system instability such as being unable to establish new IKEv2 VPN sessions. A manual reboot of the device is required to recover from this condition.

Impact

European organizations relying on Cisco IOS, IOS XE, ASA, and FTD devices for VPN connectivity and network security are at risk of service disruption due to this vulnerability. The denial of service caused by device reloads or memory exhaustion can interrupt critical business operations, especially for organizations with remote workforce or inter-office VPNs. Loss of VPN connectivity can expose organizations to operational downtime, reduced productivity, and potential security risks if fallback or alternative communication channels are less secure. Critical infrastructure sectors such as finance, healthcare, government, and telecommunications in Europe often use Cisco equipment extensively, amplifying the potential impact. Additionally, the need for manual reboot to recover from the DoS condition may increase incident response times and operational costs. The vulnerability could also be leveraged as part of a larger attack campaign to degrade network defenses or create distraction while other attacks are conducted. Given the lack of authentication or user interaction required, attackers can launch attacks remotely and anonymously, increasing the threat surface. The disruption of VPN services could also affect compliance with data protection regulations like GDPR if secure communications are compromised or interrupted.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-ios-dos-DOESHWHy (opens in a new tab)

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 14 Aug 2025, 17:06 UTC

Technical details

References

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