CVE-2026-91123

HIGHPre-NVD 7.27.2—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (19th 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
7.2EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 7.2Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

CVSS v3
7.2
EG Score
7.2HIGHmedium confidence
EG Risk
37
EG Risk 37/100CISA 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
Severity72% × 45%
Exploitation0% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
19th
KEV
Not listed

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

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). 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

September 24, 2026

Last Modified

September 24, 2026

Advisory Details (6)

Auto-updated Sep 24, 2026
Patch available. Sources: github, github_pr, github_commit.
github_commit

commit 142f5155ad8e (discourse/discourse)

Fix landed in discourse/discourse commit 142f5155ad8e — awaiting tagged release

https://github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579
github_commit

commit 0b5a27e68992 (discourse/discourse)

Fix landed in discourse/discourse commit 0b5a27e68992 — awaiting tagged release

https://github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be
github_commit

commit 097ce5600a2d (discourse/discourse)

Fix landed in discourse/discourse commit 097ce5600a2d — awaiting tagged release

https://github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24
github_commit

commit 042d7b159bed (discourse/discourse)

Fix landed in discourse/discourse commit 042d7b159bed — awaiting tagged release

https://github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318
github_pr

Security fixes for main

Fix merged in discourse/discourse PR #42882 on 2026-08-25 — awaiting tagged release

https://github.com/discourse/discourse/pull/42882
github Patch Available

Reject literal backslash path separators in iframe src traversal guard · Advisory · discourse/discourse · GitHub

https://github.com/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 19× 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. 2026-10-04 01:14 UTCEG score recompute
  2. 2026-10-03 00:55 UTCEG score recompute
  3. 2026-10-02 00:36 UTCEG score recompute
  4. 2026-10-01 19:51 UTCEPSS rescore
  5. 2026-10-01 00:16 UTCEG score recompute
  6. 2026-09-30 15:04 UTCEPSS rescore
  7. 2026-09-29 23:54 UTCEG score recompute
  8. 2026-09-29 08:25 UTCEG score recompute
  9. 2026-09-28 20:16 UTCEG score recompute
  10. 2026-09-28 13:52 UTCEPSS rescore
  11. 2026-09-28 13:52 UTCEPSS rescore
  12. 2026-09-27 19:57 UTCEG score recompute
  13. 2026-09-27 13:49 UTCEPSS rescore
  14. 2026-09-26 19:37 UTCEG score recompute
  15. 2026-09-26 15:59 UTCEPSS rescore
  16. 2026-09-26 07:25 UTCEG score recompute
  17. 2026-09-24 17:33 UTCEG score recompute
  18. 2026-09-24 17:02 UTCEG score recompute
  19. 2026-09-24 17:01 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-91123?
CVE-2026-91123 is a high vulnerability published on September 24, 2026. Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser…
When was CVE-2026-91123 disclosed?
CVE-2026-91123 was first published on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-91123 actively exploited?
CVE-2026-91123 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (19th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-91123?
CVE-2026-91123 has a CVSS base score of 7.2 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-91123?
A fix for CVE-2026-91123 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-91123

Explore →

Is Your Infrastructure Affected by CVE-2026-91123?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs