Cyber Resilience

CVE-2026-56021

Webmin ≤ 1.290

Published
18 June 2026
Modified
11 August 2026
Patch / advisory
View advisory
CVSS Score v4 6.9
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/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 0.0048 39th percentile
Risk Priority 41 floored blend · peak EPSS

Summary

CVE-2026-56021 is a medium-severity Incorrect Regular Expression (CWE-185) vulnerability in Webmin Webmin. Its CVSS base score is 6.9 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked at the 39th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Webmin allows unauthenticated attackers to read the contents of any file ending in .conf within module directories, due to a bypassable regex pattern.

CWE(s)
CWE-185CWE-777

Related Threats

MITRE ATT&CK Enterprise Techniques

T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1566 Phishing Initial Access
Adversaries may send phishing messages to gain access to victim systems.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2022-36446Same product: Webmin Webmin
CVE-2019-15107Same product: Webmin Webmin
CVE-2024-12828Same product: Webmin Webmin
CVE-2019-12840Same product: Webmin Webmin
CVE-2024-36452Same product: Webmin Webmin
CVE-2023-38303Same product: Webmin Webmin
CVE-2023-38310Same product: Webmin Webmin
CVE-2023-40985Same product: Webmin Webmin
CVE-2023-38307Same product: Webmin Webmin
CVE-2023-52046Same product: Webmin Webmin

Affected Assets

webmin
webmin
≤ 1.290

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover regex that fails to match or compare data as intended.

SI-10 Information Input Validation good match

SI-10 requires validation of inputs; correct implementation forces anchored regexes that fully neutralize the described weakness.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented development standards and tools reduces the chance that incorrect regular expressions are written into validation or filtering logic.

SA-3 System Development Life Cycle partial match

An SDLC that incorporates security can embed reviews or tooling that catch malformed regular expressions before deployment.

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 correct regex design, testing, and review to avoid improper matching.

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 in development can detect regex-related flaws before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes validation of input-handling constructs such as regex.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate correct regex design and testing.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly address proper construction and review of regular expressions.

References