CVE-2026-28407Public exploitNetwork attack vector

Malware scan evasion via failed nested extraction

Published Feb 27, 2026 · Updated Feb 27, 2026

Archive-scanning bypass in Chainguard malcontent before 1.21.0 allows remote attackers to conceal malicious content in nested archives. The extractNestedArchive function ignores a nested extraction error and still deletes the original archive, removing its bytes from later scanning. Exploitation requires a crafted nested archive to reach a scan input; the omitted bytes can prevent detection without executing code in the scanner.

CVSS severity6.9
Medium
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Archive-scanning bypass in Chainguard malcontent before 1.21.0 allows remote attackers to conceal malicious content in nested archives. The extractNestedArchive function ignores a nested extraction error and still deletes the original archive, removing its bytes from later scanning. Exploitation requires a crafted nested archive to reach a scan input; the omitted bytes can prevent detection without executing code in the scanner.

The record

CVE
CVE-2026-28407
Published
Feb 27, 2026
Updated
Feb 27, 2026
Vendor
Chainguard
Product
malcontent
Classifications
CWE-703, T1027
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 27, 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=< 1.21.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Chainguard · malcontentversion=< 1.21.0

Published CVSS scores

6.9GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-703Improper Check or Handling of Exceptional Conditions
T1027Obfuscated Files or Information

Public exploit references

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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