VulnerabilityPublished 14 Aug 2025

CVE-2025-20254: Cisco Adaptive Security Appliance (ASA) Software · Memory Leak

Affects Cisco Adaptive Security Appliance (ASA) SoftwareSource CVE Database V5

Not known to be exploited · CVSS 5.8 Medium.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score

5.8Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 37% 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:L

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

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: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

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 26 Oct 2026.

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 or the CVSS exploit maturity 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

Affected software

Product	Affected	Fixed in
Cisco Cisco Adaptive Security Appliance (ASA) Software	Affected 9.12.1 – 9.23.1 170 affected builds	Fixed in–

AI-suggested

Immediate deployment of Cisco’s official patches or updates once available is the most effective mitigation. Organizations should monitor Cisco security advisories closely for patch releases addressing this vulnerability.
Implement network-level filtering to restrict and monitor incoming IKEv2 traffic to trusted sources only, using access control lists (ACLs) or firewall rules to limit exposure to untrusted or public networks.
Deploy rate limiting or traffic anomaly detection mechanisms on VPN gateways to detect and block abnormal volumes of IKEv2 packets that could indicate exploitation attempts.
Utilize redundant VPN gateways with load balancing and failover capabilities to minimize service disruption in case one device becomes unstable due to exploitation.
Regularly audit and update VPN configurations to ensure minimal exposure and adherence to best practices, including disabling unused VPN protocols or services.
Establish robust incident response procedures to quickly identify and respond to DoS conditions, including automated alerts for VPN service degradation and readiness for manual device reboot if necessary.
Consider network segmentation to isolate critical VPN infrastructure from less trusted network segments, reducing the attack surface.
Engage with Cisco support for guidance on interim workarounds or configuration changes that may reduce risk prior to patch availability.

Description

A vulnerability in the Internet Key Exchange Version 2 (IKEv2) module of Cisco 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 improper parsing of IKEv2 packets. An attacker could exploit this vulnerability by sending a continuous stream of crafted IKEv2 packets to an affected device. A successful exploit could allow the attacker to partially exhaust system memory, causing system instability like being unable to establish new IKEv2 VPN sessions. A manual reboot of the device is required to recover from this condition.

Impact

For European organizations, the impact of CVE-2025-20254 can be significant due to the widespread use of Cisco ASA devices in enterprise and governmental networks for VPN and firewall services. The denial of service condition caused by memory exhaustion can disrupt secure remote access, which is critical for business operations, especially in the context of increased remote work and cross-border communications within Europe. Loss of VPN connectivity can lead to operational downtime, reduced productivity, and potential exposure to additional security risks if fallback or less secure communication methods are used. Critical infrastructure sectors such as finance, healthcare, energy, and public administration that rely on Cisco ASA for secure communications are particularly vulnerable. The requirement for a manual reboot to recover from the DoS condition means that automated failover or recovery mechanisms may not be sufficient, potentially prolonging service outages. Additionally, the vulnerability can be exploited without authentication or user interaction, increasing the risk of opportunistic attacks from external threat actors. While no data confidentiality or integrity is directly compromised, the availability impact alone can cause cascading effects on dependent services and compliance with regulatory requirements such as GDPR, which mandates maintaining secure and reliable IT systems.

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

Affected software

Description

AI analysisMachine-generated, updated 14 Aug 2025, 17:10 UTC

Technical details

References

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