Boot-time code execution via insufficient image validation
Published Mar 25, 2026 · Updated Mar 25, 2026
Secure boot bypass in Cisco IOS XE Software allows attackers to execute arbitrary code at boot by loading manipulated binaries. The bootloader insufficiently validates loaded binaries, permitting altered images to pass integrity checks without satisfying the Cisco-signature requirement. Exploitation requires either physical access without authentication or local level-15 privileges and breaks the device's chain of trust.
Summary
What happened
Secure boot bypass in Cisco IOS XE Software allows attackers to execute arbitrary code at boot by loading manipulated binaries. The bootloader insufficiently validates loaded binaries, permitting altered images to pass integrity checks without satisfying the Cisco-signature requirement. Exploitation requires either physical access without authentication or local level-15 privileges and breaks the device's chain of trust.
The record
- CVE
- CVE-2026-20104
- Published
- Mar 25, 2026
- Updated
- Mar 25, 2026
- Vendor
- ClamAV
- Product
- Cisco IOS XE Software
- Classifications
- CWE-124, T1601.001
- Attack vector
- physical
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 25, 2026CVE publishedPublication date reported by the CVE source.
- Mar 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=16.12.6
- Affected versionversion=16.12.6a
- Affected versionversion=16.12.7
- Affected versionversion=16.12.8
- Affected versionversion=17.10.1
- Affected versionversion=17.11.1
- Affected versionversion=17.12.1
- Affected versionversion=17.12.2
- Affected versionversion=17.12.3
- Affected versionversion=17.12.4
- Affected versionversion=17.12.5
- Affected versionversion=17.12.6
- Affected versionversion=17.13.1
- Affected versionversion=17.14.1
- Affected versionversion=17.15.1
- Affected versionversion=17.15.2
- Affected versionversion=17.15.3
- Affected versionversion=17.15.4
- Affected versionversion=17.16.1
- Affected versionversion=17.17.1
- Affected versionversion=17.18.1
- Affected versionversion=17.18.2
- Affected versionversion=17.3.3
- Affected versionversion=17.3.4
- Affected versionversion=17.3.4b
- Affected versionversion=17.3.5
- Affected versionversion=17.3.6
- Affected versionversion=17.3.7
- Affected versionversion=17.3.8
- Affected versionversion=17.3.8a
- Affected versionversion=17.4.1
- Affected versionversion=17.5.1
- Affected versionversion=17.6.1
- Affected versionversion=17.6.1y
- Affected versionversion=17.6.2
- Affected versionversion=17.6.3
- Affected versionversion=17.6.4
- Affected versionversion=17.6.5
- Affected versionversion=17.6.5a
- Affected versionversion=17.6.6
- Affected versionversion=17.6.6a
- Affected versionversion=17.6.7
- Affected versionversion=17.6.8
- Affected versionversion=17.7.1
- Affected versionversion=17.7.1a
- Affected versionversion=17.8.1
- Affected versionversion=17.8.1a
- Affected versionversion=17.9.1
- Affected versionversion=17.9.1a
- Affected versionversion=17.9.2
- Affected versionversion=17.9.3
- Affected versionversion=17.9.4
- Affected versionversion=17.9.4a
- Affected versionversion=17.9.5
- Affected versionversion=17.9.5b
- Affected versionversion=17.9.6
- Affected versionversion=17.9.6a
- Affected versionversion=17.9.7
- Affected versionversion=17.9.8
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
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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