CVE-2025-20260Network attack vector

Scanner crash via PDF ASCII85 allocation overflow

Published Jun 18, 2025 · Updated Feb 26, 2026

Heap buffer overflow in Cisco ClamAV 1.0.0 through 1.0.8 and 1.2.0 through 1.4.2 allows remote attackers to crash the scanner via crafted PDFs. In libclamav's PDF parser, filter_ascii85decode calculates a decoded buffer as four times the input length plus one without first preventing integer overflow, allowing a wrapped allocation to be smaller than the decoded output. Triggering requires MaxFileSize of at least 1024 MB and MaxScanSize of at least 1025 MB; a scanner crash is established, while code execution remains unproven.

CVSS severity9.8
Critical
EPSS probability1.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in Cisco ClamAV 1.0.0 through 1.0.8 and 1.2.0 through 1.4.2 allows remote attackers to crash the scanner via crafted PDFs. In libclamav's PDF parser, filter_ascii85decode calculates a decoded buffer as four times the input length plus one without first preventing integer overflow, allowing a wrapped allocation to be smaller than the decoded output. Triggering requires MaxFileSize of at least 1024 MB and MaxScanSize of at least 1025 MB; a scanner crash is established, while code execution remains unproven.

The record

CVE
CVE-2025-20260
Published
Jun 18, 2025
Updated
Feb 26, 2026
Vendor
ClamAV
Product
ClamAV
Classifications
CWE-122, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 18, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.2.0
  2. Affected versionversion=1.2.1
  3. Affected versionversion=1.2.2
  4. Affected versionversion=1.2.3
  5. Affected versionversion=1.3.0
  6. Affected versionversion=1.3.1
  7. Affected versionversion=1.3.2
  8. Affected versionversion=1.4.0
  9. Affected versionversion=1.4.1
  10. Affected versionversion=1.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · ClamAVversion=1.2.0; version=1.2.1; version=1.2.2; version=1.2.3; version=1.3.0; version=1.3.1; version=1.3.2; version=1.4.0; version=1.4.1; version=1.4.2

Published CVSS scores

9.8CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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