Security readout for executives and security teams
Plain-English summary
CVE-2026-26717 affects OpenFUN Richie LMS request authentication for course-run synchronization. It compares HMAC signatures in a way that can leak timing information. A remote attacker may be able to bypass authentication, but the CVSS rates exploitation complexity as high. No CISA KEV listing is provided.
Executive priority
Treat as a near-term maintenance fix for Richie LMS environments, not an emergency unless the synchronization endpoint is internet-exposed or business-critical. Prioritize confirming exposure and applying vendor-backed updates.
Technical view
In src/richie/apps/courses/api.py, sync_course_run_from_request used a non-constant-time equality check for HMAC signature verification. This is categorized as CWE-208. The reported impact is limited confidentiality and integrity loss, no availability impact, CVSS 3.1 score 4.8.
Likely exposure
Exposure is likely limited to OpenFUN Richie LMS deployments using the affected course-run synchronization endpoint and HMAC-based request verification. The provided CVE data does not identify affected versions, packages, or CPEs, so asset owners must map local Richie deployments to upstream code history.
Exploitation context
The CVE describes a remote, unauthenticated timing attack requiring high attack complexity. Public references include a GitHub repository and Medium writeup, but the bundle does not prove active exploitation. KEV status is false.
Researcher notes
Key evidence gaps are affected versions, release mapping, and vendor advisory details. The CVE record names the vulnerable function and file, and references an upstream commit. Avoid assuming exploit-in-the-wild without KEV or cited confirmation.
Mitigation direction
- Review OpenFUN Richie upstream commit a1b5bbda3403d7debb466c303a32852925fcba5f.
- Upgrade to a vendor-recommended Richie release containing the HMAC comparison fix.
- If no release is available, follow OpenFUN guidance before backporting the referenced change.
- Restrict external access to synchronization endpoints where operationally feasible.
- Monitor application logs for abnormal synchronization requests or authentication failures.
Validation and detection
- Inventory all OpenFUN Richie LMS instances and deployed code revisions.
- Check whether src/richie/apps/courses/api.py includes constant-time HMAC comparison.
- Confirm the deployed version includes the referenced upstream commit or vendor equivalent.
- Review edge and application logs for unusual access to course synchronization paths.
- Track CVE and OpenFUN advisories for affected version clarification.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-208: Exact CWE lookup
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Open ATT&CK lookupCVE-2026-26717 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N2.22.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.8MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/openfun/richie/commit/a1b5bbda3403d7debb466c303a32852925fcba5fCVE reference
- https://github.com/Rickidevs/CVE-2026-26717CVE reference
- https://medium.com/@ordogh/cve-2026-26717-hmac-timing-attack-in-openfun-richie-lms-f04377efe83d?postPublishedType=repubCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Observable Timing Discrepancy
Observable Timing Discrepancy represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.