CVE-2025-20352VulnerabilityPublished 24 Sep 2025Updated 26 Feb 2026

CVE-2025-20352: Cisco IOS · Stack-based Buffer Overflow

Affects Cisco IOSSource CVE Database V5

Exploited in the wild · KEV due 20 Oct 2025 · 41% EPSS : apply the vendor's fix or mitigations to Cisco IOS now.

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.

KEV deadline: 20 Oct 2025 US federal agencies must patch by this date; a sensible deadline for everyone else.
EPSS: 41.5% chance of exploitation in 30 days – higher than 98% 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

t = 0 is the CVE’s publication on cve.org

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: evidence found.
Listed in CISA KEV 5 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

CVE ID reserved
by cisco
2024-10-1019:15Z, 349 days before disclosure
CVE published
on cve.org
2025-09-2417:10Z, t = 0
In Threat Radar
record ingested
2025-09-2417:20Z, 10 minutes after disclosure
Added to CISA KEV (opens in a new tab)
exploitation confirmed
2025-09-29, 5 days after disclosure
KEV remediation due
US federal deadline
2025-10-20, 26 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (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

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Check the firmware or software version for Cisco IOS in the device's admin interface against the vendor advisory.

Description

A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS Software and Cisco IOS XE Software could allow the following: An authenticated, remote attacker with low privileges could cause a denial of service (DoS) condition on an affected device that is running Cisco IOS Software or Cisco IOS XE Software. To cause the DoS, the attacker must have the SNMPv2c or earlier read-only community string or valid SNMPv3 user credentials. An authenticated, remote attacker with high privileges could execute code as the root user on an affected device that is running Cisco IOS XE Software. To execute code as the root user, the attacker must have the SNMPv1 or v2c read-only community string or valid SNMPv3 user credentials and administrative or privilege 15 credentials on the affected device. An attacker could exploit this vulnerability by sending a crafted SNMP packet to an affected device over IPv4 or IPv6 networks. This vulnerability is due to a stack overflow condition in the SNMP subsystem of the affected software. A successful exploit could allow a low-privileged attacker to cause the affected system to reload, resulting in a DoS condition, or allow a high-privileged attacker to execute arbitrary code as the root user and obtain full control of the affected system. Note: This vulnerability affects all versions of SNMP.

Impact

The impact of CVE-2025-20352 is substantial for organizations worldwide relying on Cisco IOS and IOS XE devices for critical network infrastructure. The ability for low-privileged authenticated attackers to cause denial of service can disrupt network availability, affecting business operations, communications, and services dependent on these devices. More severe is the possibility for high-privileged attackers to execute arbitrary code as root, enabling full device compromise. This could lead to interception or manipulation of network traffic, persistent backdoors, lateral movement within networks, and disruption of network control and management. Given Cisco IOS's widespread deployment in enterprise, service provider, government, and critical infrastructure networks globally, exploitation could have cascading effects on internet stability and security. The requirement for authentication limits exposure somewhat, but many organizations still use default or weak SNMP community strings, increasing risk. The vulnerability also affects IPv6-enabled environments, expanding the attack surface. Without timely patching and access controls, attackers could leverage this flaw to severely degrade or take over network infrastructure.

Mitigation

1. Immediate application of Cisco's security patches or software updates that address CVE-2025-20352 is critical. Organizations should consult Cisco's official advisories and upgrade to fixed IOS and IOS XE versions. 2. Restrict SNMP access strictly to trusted management hosts and networks using access control lists (ACLs) and firewall rules to prevent unauthorized SNMP traffic. 3. Disable SNMP services on devices where it is not required to reduce the attack surface. 4. Replace legacy SNMPv1 and SNMPv2c community strings with SNMPv3, which provides stronger authentication and encryption. 5. Enforce strong, unique SNMP community strings and credentials, avoiding default or easily guessable values. 6. Monitor SNMP traffic for anomalous or malformed packets that could indicate exploitation attempts. 7. Implement network segmentation to isolate management interfaces and reduce exposure of critical devices. 8. Conduct regular vulnerability assessments and penetration testing focused on network management protocols. 9. Maintain up-to-date inventory of affected devices and ensure all are evaluated and remediated promptly. 10. Educate network administrators on secure SNMP configuration and the risks of legacy protocols.

CWE-121Stack-based Buffer Overflow (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #14
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
Architecture and Design
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Implementation
Implement and perform bounds checking on input.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

Timeline

What to do

Description

AI analysisMachine-generated, updated 27 Feb 2026, 00:25 UTC

WeaknessesCWE-121

Technical details

References

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