Cyber Resilience

CVE-2026-21439

Badkeys ≤ 0.0.16

Public PoC
Published
06 January 2026
Modified
12 January 2026
Patch / advisory
View advisory
CVSS Score v4 2.0
Click a component to see what it means
Raw vectorCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0031 23th percentile
Risk Priority 24 floored blend · peak EPSS

Summary

CVE-2026-21439 is a low-severity Improper Neutralization of Escape, Meta, or Control Sequences (CWE-150) vulnerability in Badkeys Badkeys. Its CVSS base score is 2.0 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Content Injection (T1659); ranked at the 23th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

badkeys is a tool and library for checking cryptographic public keys for known vulnerabilities. In versions 0.0.15 and below, an attacker may inject content with ASCII control characters like vertical tabs, ANSI escape sequences, etc., that can create misleading output…

more

of the badkeys command-line tool. This impacts scanning DKIM keys (both --dkim and --dkim-dns), SSH keys (--ssh-lines mode), and filenames in various modes. This issue is fixed in version 0.0.16.

CWE(s)
CWE-150

Related Threats

MITRE ATT&CK Enterprise Techniques

T1659 Content Injection Initial Access
Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-40505Shared CWE-150
CVE-2026-49147Shared CWE-150
CVE-2026-45803Shared CWE-150
CVE-2024-36052Shared CWE-150
CVE-2025-62845Shared CWE-150
CVE-2025-65082Shared CWE-150
CVE-2024-56201Shared CWE-150
CVE-2026-26149Shared CWE-150
CVE-2023-3265Shared CWE-150
CVE-2025-0975Shared CWE-150

Affected Assets

badkeys
badkeys
≤ 0.0.16

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.2.10
  • V1.3.12

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

SI-10 requires validation/sanitization of inputs that directly stops escape/meta/control sequences from reaching downstream components.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input neutralization and escaping to prevent this class of flaw.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect the weakness but does not itself implement neutralization.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and output encoding that directly neutralizes escape/meta sequences.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for controls against injection and malformed input sequences.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles reduce attack surface but do not prescribe specific neutralization techniques.

A.8.28 Secure coding partial match
prevents

Secure coding standards require proper escaping and neutralization of control characters before downstream processing.

References