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NVD / CVE Program· CNA GitHub_M

CVE-2026-91132: Discourse: Wildcard iframe origin allowlist bypass via authority separators

Noroxi assessment

Priority: Monitor (action score 17/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.13% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • No fixed version is recorded, but the references include a patch (commit or PR) link.

Low priority for now. See the fix and affected versions sections below.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, sites using wildcard patterns in the allowed_iframes setting could accept a crafted iframe URL whose allowlisted suffix appeared after a URL authority separator. The wildcard origin check matched the allowed domain text, while browser URL parsing selected a different attacker-controlled origin. A user with posting privileges could exploit the flaw through a post or a Onebox oEmbed response and cause an attacker-controlled iframe to be rendered independently of the allowlisted domain. Successful exploitation requires a site-configured wildcard iframe pattern and the ability to create a post or trigger an oEmbed request for an attacker-controlled URL. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

MediumCVSS 4.3 · v3.1—No exploit No fix recorded
Published
Sep 24, 2026
Updated
Sep 29, 2026
EPSS
0.1% · 3th percentile

Report tools

JSON

Action score

17

Monitor

Low priority for now.

CVSS
17 / 40 · 4.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
4.3
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • discourse discourse

    • < 2026.8.0, >= 2026.7.0-latest, < 2026.7.2, >= 2026.6.0-latest, < 2026.6.3, >= 2026.1.0-latest, < 2026.1.8affected

Same product

discourse: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-41163RCE via malicious SNS subscription payload
    45Plan
  • CVE-2025-68662FinalDestination hostname matching allows SSRF protection bypass
    39Monitor
  • CVE-2023-47121Discourse SSRF vulnerability in Embedding
    39Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-91120Sep 24, 2026 · Discourse: Stored HTML injection in video notification emails
    21Monitor
  • ← EarlierCVE-2026-91121Sep 24, 2026 · Discourse: Chat upload filenames rendered as raw HTML in excerpts
    20Monitor
  • Later →CVE-2026-91134Sep 24, 2026 · Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist
    21Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-346 · Origin Validation Error

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. SSVC exploitation— → none

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records