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: 0.6% (46th percentile of EPSS-scored CVEs). 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: 0.6%CVSS: 5.3Exploit: None knownExposed services: Not assessed

The CVE record names the fixed release — apply it.

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
5.3MEDIUMmedium confidence
EG Risk
39
EG Risk 39/100CISA SSVC

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%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
46th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 10, 2026

Last Modified

September 8, 2026

Advisory Details (9)

Auto-updated Aug 10, 2026
Fix named in the CVE record. Sources: github_pr, github, github_commit.
githubMentions a patch (unverified)

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 10× in last 7d / 40× 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. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:13 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
  4. 2026-10-06 18:21 UTCEG score recompute
  5. 2026-10-06 15:18 UTCEPSS rescore
  6. 2026-10-05 17:43 UTCEPSS rescore
  7. 2026-10-05 07:48 UTCEG score recompute
  8. 2026-10-04 23:22 UTCEPSS rescore
  9. 2026-10-04 04:26 UTCEG score recompute
  10. 2026-10-03 14:26 UTCEPSS rescore
  11. 2026-10-02 09:19 UTCEG score recompute
  12. 2026-10-01 19:50 UTCEPSS rescore
  13. 2026-09-30 22:36 UTCEG score recompute
  14. 2026-09-29 05:22 UTCEG score recompute
  15. 2026-09-28 13:52 UTCEPSS rescore
  16. 2026-09-27 13:48 UTCEPSS rescore
  17. 2026-09-27 12:45 UTCEG score recompute
  18. 2026-09-26 15:59 UTCEPSS rescore
  19. 2026-09-25 04:01 UTCEG score recompute
  20. 2026-09-23 21:10 UTCEG score recompute
  21. 2026-09-23 17:54 UTCEPSS rescore
  22. 2026-09-22 15:23 UTCEG score recompute
  23. 2026-09-21 21:09 UTCEPSS rescore
  24. 2026-09-21 13:05 UTCEG score recompute
  25. 2026-09-20 20:16 UTCEPSS rescore
Show 74 more
  1. 2026-09-20 10:48 UTCEG score recompute
  2. 2026-09-19 05:19 UTCEG score recompute
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 03:02 UTCEG score recompute
  5. 2026-09-17 00:45 UTCEG score recompute
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 05:15 UTCEPSS rescore
  8. 2026-09-15 13:46 UTCEG score recompute
  9. 2026-09-15 03:12 UTCEPSS rescore
  10. 2026-09-14 11:09 UTCEG score recompute
  11. 2026-09-13 08:53 UTCEG score recompute
  12. 2026-09-12 15:02 UTCEPSS rescore
  13. 2026-09-12 06:36 UTCEG score recompute
  14. 2026-09-11 14:53 UTCEPSS rescore
  15. 2026-09-11 04:18 UTCEG score recompute
  16. 2026-09-10 09:35 UTCEPSS rescore
  17. 2026-09-10 02:01 UTCEG score recompute
  18. 2026-09-08 22:01 UTCEPSS rescore
  19. 2026-09-07 17:17 UTCEG score recompute
  20. 2026-09-06 13:48 UTCEPSS rescore
  21. 2026-09-06 12:57 UTCEG score recompute
  22. 2026-09-05 10:40 UTCEG score recompute
  23. 2026-09-04 08:22 UTCEG score recompute
  24. 2026-09-04 05:07 UTCEPSS rescore
  25. 2026-09-03 03:07 UTCEG score recompute
  26. 2026-09-02 14:12 UTCEPSS rescore
  27. 2026-09-02 00:45 UTCEG score recompute
  28. 2026-09-01 13:54 UTCEPSS rescore
  29. 2026-09-01 04:40 UTCEPSS rescore
  30. 2026-09-01 04:40 UTCEPSS rescore
  31. 2026-08-31 22:11 UTCEG score recompute
  32. 2026-08-30 19:18 UTCEPSS rescore
  33. 2026-08-30 19:17 UTCEPSS rescore
  34. 2026-08-30 12:15 UTCEG score recompute
  35. 2026-08-30 01:22 UTCEPSS rescore
  36. 2026-08-29 09:58 UTCEG score recompute
  37. 2026-08-28 21:42 UTCEPSS rescore
  38. 2026-08-28 06:21 UTCEG score recompute
  39. 2026-08-27 14:25 UTCEPSS rescore
  40. 2026-08-27 03:59 UTCEG score recompute
  41. 2026-08-26 14:47 UTCEPSS rescore
  42. 2026-08-26 01:41 UTCEG score recompute
  43. 2026-08-25 13:49 UTCEPSS rescore
  44. 2026-08-24 23:25 UTCEG score recompute
  45. 2026-08-23 21:08 UTCEG score recompute
  46. 2026-08-23 00:19 UTCEPSS rescore
  47. 2026-08-22 18:51 UTCEG score recompute
  48. 2026-08-21 23:49 UTCEPSS rescore
  49. 2026-08-21 16:34 UTCEG score recompute
  50. 2026-08-20 22:56 UTCEPSS rescore
  51. 2026-08-20 14:17 UTCEG score recompute
  52. 2026-08-19 17:04 UTCEPSS rescore
  53. 2026-08-19 11:37 UTCEG score recompute
  54. 2026-08-18 13:49 UTCEPSS rescore
  55. 2026-08-18 13:49 UTCEPSS rescore
  56. 2026-08-18 09:20 UTCEG score recompute
  57. 2026-08-17 13:47 UTCEPSS rescore
  58. 2026-08-17 07:04 UTCEG score recompute
  59. 2026-08-16 14:56 UTCEPSS rescore
  60. 2026-08-16 14:56 UTCEPSS rescore
  61. 2026-08-16 04:47 UTCEG score recompute
  62. 2026-08-16 02:15 UTCEPSS rescore
  63. 2026-08-15 02:29 UTCEG score recompute
  64. 2026-08-15 01:31 UTCEPSS rescore
  65. 2026-08-14 00:13 UTCEG score recompute
  66. 2026-08-13 22:00 UTCEPSS rescore
  67. 2026-08-12 21:55 UTCEG score recompute
  68. 2026-08-12 13:51 UTCEPSS rescore
  69. 2026-08-11 19:38 UTCEG score recompute
  70. 2026-08-10 17:22 UTCEG score recompute
  71. 2026-08-10 17:10 UTCEG score recompute
  72. 2026-08-10 16:29 UTCEG score recompute
  73. 2026-08-10 16:10 UTCEG score recompute
  74. 2026-08-10 16:09 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

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 on August 10, 2026, with the most recent update on September 8, 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 0.6% probability of exploitation in the next 30 days (46th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-72721?
CVE-2026-72721 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-72721?
The CVE record for CVE-2026-72721 names the fix: "This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0."

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