Cyber Resilience

CVE-2026-21840

Published
14 July 2026
Modified
15 July 2026
CVSS Score v3.1 3.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.0015 5th percentile
Risk Priority 15 floored blend · peak EPSS

Summary

CVE-2026-21840 is a low-severity Observable Timing Discrepancy (CWE-208) vulnerability in Hcl Software (inferred from references). Its CVSS base score is 3.1 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Account Discovery (T1087); ranked at the 5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

HCL BigFix Platform is affected by a user enumeration vulnerability which might allow an attacker, through careful system control and response time monitoring, to perform some level of user enumeration for the BigFix service.

CWE(s)
CWE-208

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1087 Account Discovery Discovery
Adversaries may attempt to get a listing of valid accounts, usernames, or email addresses on a system or within a compromised environment.
attack.mitre.org →
Why these techniques?

CWE-208 timing-based user enumeration directly enables account discovery on the BigFix service.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-41263Shared CWE-208
CVE-2026-41161Shared CWE-208
CVE-2026-48011Shared CWE-208
CVE-2026-41418Shared CWE-208
CVE-2026-32702Shared CWE-208
CVE-2026-40263Shared CWE-208
CVE-2026-54685Shared CWE-208
CVE-2026-48859Shared CWE-208
CVE-2026-39321Shared CWE-208
CVE-2026-44368Shared CWE-208

Affected Assets

Hcl Software
—
inferred from references and description; NVD did not file a CPE for this CVE

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)
  • V11.2.4

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SC-30 Concealment and Misdirection
addresses: CWE-208

Timing randomization or delays can mask true operation timing and mislead timing-based attacks.

SC-31 Covert Channel Analysis
addresses: CWE-208

Observable timing discrepancies are a primary mechanism for constructing covert timing channels; analysis identifies and bounds them, limiting exploitation.

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 constant-time implementations that eliminate observable timing discrepancies.

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.8.17 Clock synchronization none match
none

Consistent reference clocks limit the attacker's ability to measure or manipulate timing differences that could reveal internal state or processing paths.

References