CVE-2025-20327VulnerabilityPublished 24 Sep 2025

CVE-2025-20327: Cisco IOS · Improper Validation of Specified Type of Input

Affects Cisco IOSSource CVE Database V5

Not known to be exploited · CVSS 7.7 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.7High

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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 24 Sep 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 2026-10-25.

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 mitigation should focus on restricting access to the Cisco IOS web UI management interface to trusted administrators only, ideally via secure management VLANs or out-of-band management networks. 2. Implement strong authentication controls, including multi-factor authentication (MFA), to reduce the risk of credential compromise. 3. Monitor network devices for unusual reloads or HTTP request patterns targeting the web UI, and enable logging to detect potential exploitation attempts. 4. Apply network segmentation to isolate critical infrastructure devices from general user networks to limit exposure. 5. Since no patches are currently listed, maintain close coordination with Cisco for timely release and deployment of security updates addressing this vulnerability. 6. Consider disabling the web UI management interface if not strictly necessary, switching to more secure management protocols such as SSH or dedicated management tools. 7. Conduct regular vulnerability assessments and penetration tests focusing on network device management interfaces to proactively identify and remediate weaknesses. 8. Educate network administrators about this vulnerability and the importance of safeguarding credentials and access to management interfaces.

Description

A vulnerability in the web UI of Cisco IOS Software could allow an authenticated, remote attacker with low privileges to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper input validation. An attacker could exploit this vulnerability by sending a crafted URL in an HTTP request. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

Impact

For European organizations, this vulnerability poses a significant risk to network infrastructure stability and availability. Cisco IOS is widely deployed across enterprise, service provider, and governmental networks in Europe, forming the backbone of critical communications and data routing. A successful exploit could cause routers or switches to reload unexpectedly, leading to network outages, degraded service, and potential disruption of business-critical applications. This is particularly impactful for sectors relying on continuous network uptime such as finance, healthcare, telecommunications, and public administration. The requirement for authentication limits exploitation to insiders or attackers who have obtained valid credentials, but the low privilege requirement means even less-privileged users could trigger the DoS. The resulting downtime could affect data center connectivity, branch office communications, and internet access, potentially causing cascading operational impacts and financial losses. Additionally, the vulnerability could be leveraged as part of a broader attack campaign to disrupt services or as a diversion tactic during more sophisticated intrusions.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-invalid-url-dos-Nvxszf6u (opens in a new tab)

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 24 Sep 2025, 17:21 UTC

Technical details

References

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