CVE-2026-27166

MEDIUMNVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.4 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 91% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes.

CVSS v3
5.4
EG Score
5.4(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity54% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
9%
KEV
Not listed

Published

March 19, 2026

Last Modified

June 17, 2026

Advisory Details (2)

Auto-updated Aug 6, 2026
Patch available. Sources: github_commit, github.
github Patch Available

HTML injection via prohibited iframe URLs · Advisory · discourse/discourse · GitHub

https://github.com/discourse/discourse/security/advisories/GHSA-h653-cq78-vjj2
github_commit Patch Available

commit c4762a4fac2f (discourse/discourse)

Patch available: discourse/discourse _gh-attach-assets (contains commit c4762a4fac2f)

https://github.com/discourse/discourse/commit/c4762a4fac2f61f52f325396b11d3aeb955ea925

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 26× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 19:27 UTCEPSS rescore
  3. 2026-09-17 19:30 UTCEPSS rescore
  4. 2026-09-16 14:08 UTCEPSS rescore
  5. 2026-09-16 05:15 UTCEPSS rescore
  6. 2026-09-13 16:47 UTCEPSS rescore
  7. 2026-09-12 15:01 UTCEPSS rescore
  8. 2026-09-11 14:52 UTCEPSS rescore
  9. 2026-09-10 09:34 UTCEPSS rescore
  10. 2026-09-08 22:00 UTCEPSS rescore
  11. 2026-09-07 16:01 UTCEPSS rescore
  12. 2026-09-06 13:47 UTCEPSS rescore
  13. 2026-09-06 13:47 UTCEPSS rescore
  14. 2026-09-04 05:06 UTCEPSS rescore
  15. 2026-09-02 17:38 UTCOSV refresh
  16. 2026-09-02 14:11 UTCEPSS rescore
  17. 2026-09-01 13:53 UTCEPSS rescore
  18. 2026-09-01 04:39 UTCEPSS rescore
  19. 2026-08-30 19:17 UTCEPSS rescore
  20. 2026-08-30 01:22 UTCEPSS rescore
  21. 2026-08-28 21:41 UTCEPSS rescore
  22. 2026-08-27 14:25 UTCEPSS rescore
  23. 2026-08-26 14:46 UTCEPSS rescore
  24. 2026-08-25 13:48 UTCEPSS rescore
  25. 2026-08-21 23:49 UTCEPSS rescore
Show 34 more
  1. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-19 17:03 UTCEPSS rescore
  3. 2026-08-18 13:48 UTCEPSS rescore
  4. 2026-08-17 13:47 UTCEPSS rescore
  5. 2026-08-16 14:56 UTCEPSS rescore
  6. 2026-08-16 11:09 UTCEG score recompute
  7. 2026-08-16 02:14 UTCEPSS rescore
  8. 2026-08-15 01:30 UTCEPSS rescore
  9. 2026-08-14 07:19 UTCEG score recompute
  10. 2026-08-13 22:00 UTCEPSS rescore
  11. 2026-08-12 22:04 UTCEG score recompute
  12. 2026-08-12 13:50 UTCEPSS rescore
  13. 2026-08-11 13:42 UTCEPSS rescore
  14. 2026-08-11 05:39 UTCEG score recompute
  15. 2026-08-11 00:00 UTCEPSS rescore
  16. 2026-08-10 06:26 UTCEG score recompute
  17. 2026-08-09 13:46 UTCEPSS rescore
  18. 2026-08-09 06:53 UTCEG score recompute
  19. 2026-08-08 16:37 UTCEPSS rescore
  20. 2026-08-07 17:22 UTCEG score recompute
  21. 2026-08-06 13:46 UTCEPSS rescore
  22. 2026-08-06 01:33 UTCEG score recompute
  23. 2026-08-05 19:17 UTCEPSS rescore
  24. 2026-08-04 15:10 UTCEPSS rescore
  25. 2026-08-04 00:41 UTCEG score recompute
  26. 2026-08-03 10:36 UTCEPSS rescore
  27. 2026-08-02 16:33 UTCEG score recompute
  28. 2026-08-02 02:26 UTCEPSS rescore
  29. 2026-08-01 04:16 UTCEPSS rescore
  30. 2026-07-30 16:27 UTCEPSS rescore
  31. 2026-07-30 01:30 UTCEPSS rescore
  32. 2026-07-28 15:36 UTCEPSS rescore
  33. 2026-07-27 14:38 UTCEG score recompute
  34. 2026-07-27 14:27 UTCOSV refresh

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-27166?
CVE-2026-27166 is a medium vulnerability published on March 19, 2026. Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions…
When was CVE-2026-27166 disclosed?
CVE-2026-27166 was first published in the National Vulnerability Database on March 19, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-27166 actively exploited?
CVE-2026-27166 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 91.5% of all scored CVEs.
What is the CVSS score of CVE-2026-27166?
CVE-2026-27166 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-27166?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-27166, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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