Cyber Resilience

CVE-2026-26717

Published
25 February 2026
Modified
15 April 2026
CVSS Score v3.1 4.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS Score 0.0038 30th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-26717 is a medium-severity Observable Timing Discrepancy (CWE-208) vulnerability. Its CVSS base score is 4.8 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 30th 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 AC-3 (Access Enforcement) and SC-13 (Cryptographic Protection) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

An issue in OpenFUN Richie (LMS) in src/richie/apps/courses/api.py. The application used the non-constant time == operator for HMAC signature verification in the sync_course_run_from_request function. This allows remote attackers to forge valid signatures and bypass authentication by measuring response time discrepancies

CWE(s)
CWE-208

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

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 →
Why these techniques?

Timing attack on HMAC verification directly enables authentication bypass against a public-facing LMS API endpoint (sync_course_run_from_request).

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

CVEs Like This One

CVE-2026-40972Shared CWE-208
CVE-2026-44061Shared CWE-208
CVE-2025-68621Shared CWE-208
CVE-2026-33006Shared CWE-208
CVE-2026-13183Shared CWE-208
CVE-2024-42512Shared CWE-208
CVE-2026-27882Shared CWE-208
CVE-2026-28464Shared CWE-208
CVE-2026-5086Shared CWE-208
CVE-2026-28475Shared CWE-208

Affected Assets

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SC-13 Cryptographic Protection
  • AC-3 Access Enforcement
  • SA-8 Security and Privacy Engineering Principles
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V11.2.4

Mitigating Controls (NIST 800-53 r5) AI

SC-13 Cryptographic Protection good match
prevent

Mandates approved cryptographic mechanisms for protecting information authenticity; correct HMAC verification requires constant-time comparison to block timing attacks.

AC-3 Access Enforcement good match
prevent

Enforces access control decisions via verified signatures; the non-constant-time comparison directly allows forged signatures to bypass enforcement.

SA-8 Security and Privacy Engineering Principles partial match
prevent

Requires engineering principles that include constant-time algorithms when implementing sensitive comparisons such as HMAC signature checks.

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