CVE-2026-72721

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% 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, secondary
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: 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 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: 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
Severity53% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

August 10, 2026

Last Modified

August 10, 2026

Advisory Details (9)

Auto-updated Aug 10, 2026
Patch available. Sources: github_pr, github, github_commit.
github Patch Available

Onebox Domain Blocklist Bypass via Case-Sensitive Comparison · Advisory · discourse/discourse · GitHub

https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6
github_pr

Security fixes for release/2026.6

Fix merged in discourse/discourse PR #42094 on 2026-07-28 — awaiting tagged release

https://github.com/discourse/discourse/pull/42094
github_pr

Security fixes for release/2026.5

Fix merged in discourse/discourse PR #42093 on 2026-07-28 — awaiting tagged release

https://github.com/discourse/discourse/pull/42093
github_pr

Security fixes for release/2026.1

Fix merged in discourse/discourse PR #42092 on 2026-07-28 — awaiting tagged release

https://github.com/discourse/discourse/pull/42092
github_pr

Security fixes for main

Fix merged in discourse/discourse PR #42091 on 2026-07-28 — awaiting tagged release

https://github.com/discourse/discourse/pull/42091
github_commit

commit f503971d311b (discourse/discourse)

Fix landed in discourse/discourse commit f503971d311b — awaiting tagged release

https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5
github_commit

commit caa615c371b1 (discourse/discourse)

Fix landed in discourse/discourse commit caa615c371b1 — awaiting tagged release

https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584
github_commit

commit c2eb6b0e5597 (discourse/discourse)

Fix landed in discourse/discourse commit c2eb6b0e5597 — awaiting tagged release

https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd
github_commit

commit a3e10759fef4 (discourse/discourse)

Fix landed in discourse/discourse commit a3e10759fef4 — awaiting tagged release

https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 33× 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. 2026-08-26 01:41 UTCEG score recompute
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 23:25 UTCEG score recompute
  4. 2026-08-23 21:08 UTCEG score recompute
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-22 18:51 UTCEG score recompute
  7. 2026-08-21 23:49 UTCEPSS rescore
  8. 2026-08-21 16:34 UTCEG score recompute
  9. 2026-08-20 22:56 UTCEPSS rescore
  10. 2026-08-20 14:17 UTCEG score recompute
  11. 2026-08-19 17:04 UTCEPSS rescore
  12. 2026-08-19 11:37 UTCEG score recompute
  13. 2026-08-18 13:49 UTCEPSS rescore
  14. 2026-08-18 13:49 UTCEPSS rescore
  15. 2026-08-18 09:20 UTCEG score recompute
  16. 2026-08-17 13:47 UTCEPSS rescore
  17. 2026-08-17 07:04 UTCEG score recompute
  18. 2026-08-16 14:56 UTCEPSS rescore
  19. 2026-08-16 14:56 UTCEPSS rescore
  20. 2026-08-16 04:47 UTCEG score recompute
  21. 2026-08-16 02:15 UTCEPSS rescore
  22. 2026-08-15 02:29 UTCEG score recompute
  23. 2026-08-15 01:31 UTCEPSS rescore
  24. 2026-08-14 00:13 UTCEG score recompute
  25. 2026-08-13 22:00 UTCEPSS rescore
Show 8 more
  1. 2026-08-12 21:55 UTCEG score recompute
  2. 2026-08-12 13:51 UTCEPSS rescore
  3. 2026-08-11 19:38 UTCEG score recompute
  4. 2026-08-10 17:22 UTCEG score recompute
  5. 2026-08-10 17:10 UTCEG score recompute
  6. 2026-08-10 16:29 UTCEG score recompute
  7. 2026-08-10 16:10 UTCEG score recompute
  8. 2026-08-10 16:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-72721?
CVE-2026-72721 is a medium vulnerability published on August 10, 2026. Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.isblocked? compares hostnames and SiteSetting.blockedonebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing…
When was CVE-2026-72721 disclosed?
CVE-2026-72721 was first published in the National Vulnerability Database on August 10, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-72721 actively exploited?
CVE-2026-72721 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 64.5% of all scored CVEs.
What is the CVSS score of CVE-2026-72721?
CVE-2026-72721 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-72721?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-72721, 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.

Dependency Blast Radius

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