CVE-2026-20337

HIGH

ClamAV ZIP File Format Processing Memory Corruption Vulnerability

Title source: CVE List
Search associated code STIX 2.1 vulnerability STIX 2.1 with PoCs

Record summary

CVE-2026-20337 has a selected CVSS score of 7.5 (high); EIP currently links 1 curated repository PoC.

Description

A vulnerability in the zip archive parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition on an affected device. This vulnerability is due to improper boundary checks for content in zip files during scanning, which may result in an out-of-bounds write condition. An attacker could exploit this vulnerability by submitting a crafted zip file for scanning. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.

Description source: CVE List

Exploitation context

Available material

Curated repository PoCs
1

CISA SSVC decision

ExploitationNone
AutomatableYes
Technical impactPartial

CISA Coordinator · SSVC 2.0.3 · Evaluated Aug 7, 2026 · Source: CVE List

Affected products and versions

1
ProductSourceVersion range

Cisco Secure Endpoint

Browse Cisco / Cisco Secure Endpoint

Default status: unknown

CVE List7.0.5affected
6.2.19affected
7.3.3affected
7.2.13affected
6.1.5affected
6.3.1affected
6.2.5affected
7.3.5affected
6.2.1affected
7.2.7affected
7.1.1affected
6.3.5affected
Showing 12 of 146 version ranges

Proofs of concept

1

Curated repository PoCs

GitHubCVE-2026-20348Curated repository PoCby exploitintel8Exploit6 files

C · 22.3 KiB · linked to 2 vulnerabilities

GitHub
PoC details
Analysisdeepseek-v4-pro:cloud ·

Technical assessment

A Python 3 exploit for CVE-2026-20348 that crafts a malicious XAR file to trigger an out-of-bounds memory allocation in ClamAV's XAR parser, causing a denial-of-service via OOM kill. The script generates the payload, stages it in a Docker container, executes clamscan, and verifies the process was killed by SIGKILL.

Backdoor review

No backdoor observed in reviewed code

The PoC for CVE-2026-20348 consists of a Python script that generates a crafted XAR file and uses Docker to trigger a memory-exhaustion DoS in a vulnerable ClamAV container. The script performs only the described exploit behavior: it builds a XAR with a large declared TOC, stages it into a container, runs clamscan, and checks for an OOM-kill signal. No backdoor, concealed payload, or operator-directed harm is present.

ClassificationExploit
Model confidence98%
AuthenticationNot required
Languagespython
Target softwareClamAV
Attack typesdenial-of-service
Evidence & reasoningClassification basis · observed behavior · safety review
Technical evidence

Classification basis and observed behavior

Classification basis

The artifact is classified as an exploit because it contains code (poc/poc.py) that actively crafts a malicious input and executes it against a target to trigger a vulnerability, resulting in a denial-of-service condition. The README and verification report confirm its purpose is to exercise the vulnerability, not just detect it.

README.md:1poc/poc.py:1-3poc_verification_report.md:1

Requirements

  • A running Docker container of a vulnerable ClamAV version (<= 1.5.3) with a memory cap.poc/poc.py:99-105

Observed behavior

  • Crafts a XAR file with a header declaring a decompressed TOC size just under 1 GiB and a compressed TOC of ~1 MB.poc/poc.py:68-84
  • Stages the crafted XAR file and a minimal signature database into the target Docker container.poc/poc.py:122-129
  • Executes clamscan on the crafted file inside the container and checks for exit code 137 (SIGKILL) and the container's OOMKilled flag to confirm successful exploitation.poc/poc.py:134-158
Safety-review evidence

Behaviors behind the backdoor verdict

Observables

Docker Exec
Payload withheldThe PoC uses docker exec to run clamscan inside a lab container, which is the expected delivery mechanism for the DoS trigger.poc/poc.py:135-136
File Write
Payload withheldThe script writes a crafted XAR file to a temporary directory; this is the exploit payload generation, not a backdoor.poc/poc.py:68-84
Review boundaries

What the analysis did not establish

  • Evidence coverage is COMPLETE_FOR_READABLE_SELECTED_TEXT; 3 unclassified binary files totaling 7772 bytes were not analyzed.
  • The analysis is based solely on static review of the provided source code and documentation; the code was not executed.
  • Binary files (e.g., the crafted XAR) are not inspected; the review covers only the provided readable text.
  • The analysis does not verify the correctness or safety of the exploit against the target; it only assesses the PoC for backdoor behavior.
Model interpretation

This review is limited to the supplied PoC code and context. It does not assert that the code works or is safe to execute.

References

2