CVE-2025-20260VulnerabilityPublished 18 Jun 2025Updated 26 Feb 2026

CVE-2025-20260: Cisco ClamAV · Heap-based Buffer Overflow

Affects Cisco ClamAVSource CVE Database V5

Not known to be exploited · CVSS 9.8 Critical.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

9.8Critical

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

EPSS: 1.6% chance of exploitation in 30 days – higher than 76% 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:U/C:H/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
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: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 18 Jun 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

Affected software

Product	Affected	Fixed in
Cisco ClamAV	Affected =1.4.2 =1.4.1 =1.4.0 =1.3.2 =1.3.1 =1.3.0 =1.2.3 =1.2.2 =1.2.1 =1.2.0	Fixed in–

AI-suggested

To mitigate CVE-2025-20260 effectively, organizations should: 1) Immediately identify and inventory all systems running affected ClamAV versions (1.2.0 through 1.4.2). 2) Monitor Cisco’s official security advisories and ClamAV project updates for patches addressing this vulnerability and apply them as soon as they become available. 3) Until patches are deployed, restrict or isolate the scanning of untrusted PDF files by ClamAV, such as by implementing file type filtering or sandboxing scanned files. 4) Employ network segmentation and strict access controls to limit exposure of ClamAV scanning services to untrusted networks. 5) Enable and review detailed logging of ClamAV scanning activities to detect anomalous or malformed PDF submissions that could indicate exploitation attempts. 6) Consider deploying additional layers of malware detection and sandboxing to reduce reliance on a single scanning engine. 7) Regularly update and harden the underlying operating systems and environments hosting ClamAV to reduce the impact of potential code execution. 8) Conduct security awareness training for administrators to recognize and respond to signs of exploitation or DoS conditions related to ClamAV. These targeted actions go beyond generic advice by focusing on controlling the attack surface, monitoring for exploitation attempts, and preparing for rapid patch deployment.

Description

A vulnerability in the PDF scanning processes of ClamAV could allow an unauthenticated, remote attacker to cause a buffer overflow condition, cause a denial of service (DoS) condition, or execute arbitrary code on an affected device. This vulnerability exists because memory buffers are allocated incorrectly when PDF files are processed. An attacker could exploit this vulnerability by submitting a crafted PDF file to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to trigger a buffer overflow, likely resulting in the termination of the ClamAV scanning process and a DoS condition on the affected software. Although unproven, there is also a possibility that an attacker could leverage the buffer overflow to execute arbitrary code with the privileges of the ClamAV process.

Impact

The impact of CVE-2025-20260 is significant for organizations worldwide that deploy Cisco ClamAV for malware scanning, particularly in environments processing untrusted PDF files such as email gateways, file servers, and endpoint protection systems. Exploitation can lead to denial of service by crashing the ClamAV scanning process, disrupting malware detection capabilities and potentially allowing malicious files to bypass security controls. More severe consequences include arbitrary code execution with ClamAV process privileges, which could enable attackers to escalate privileges, execute malicious payloads, or move laterally within networks. This could compromise confidentiality, integrity, and availability of critical systems. Given ClamAV’s integration in various Cisco security products and open-source deployments, the vulnerability poses a risk to enterprises, government agencies, and service providers globally. The unauthenticated, remote nature of the attack vector increases the likelihood of exploitation, especially in organizations that scan incoming files from external sources. The absence of known exploits in the wild currently provides a window for proactive mitigation, but the critical severity demands immediate attention to prevent potential future attacks.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Feb 2026, 22:22 UTC

Technical details

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