NVD / CVE Program· CNA GitHub_M

CVE-2023-28440: Denial of service via admin theme import route in Discourse

Noroxi assessment

Priority: Monitor (action score 10/100)

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: 0.68% (FIRST EPSS); higher than 52.7% of all records.
Anyone who can reach it over the internet can trigger it. Administrator privileges are required. No user action is required. No special conditions are required; it is repeatable.
According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

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 platform for community discussion. In affected versions a maliciously crafted request from a Discourse administrator can lead to a long-running request and eventual timeout. This has the greatest potential impact in shared hosting environments where admins are untrusted. This issue has been addressed in versions 3.0.3 and 3.1.0.beta4. Users are advised to upgrade. There are no known workarounds for this vulnerability.

LowCVSS 2.7 · v3.1—No exploit No fix recorded

Denial of service

Published: Apr 18, 2023
Updated: Jun 17, 2026
EPSS: 0.6% · 52th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 10 / 40 · 2.7 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.6%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 2.7
CNA · GitHub_M: 2.7; agree

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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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.

Vendor	Product	CPE
discourse	discourse	cpe:2.3:a:discourse:discourse

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

discourse discoursebefore 3.0.3
discourse discourse1.1.0
discourse discourse1.2.0
discourse discourse1.3.0
discourse discourse1.4.0
discourse discourse1.5.0
discourse discourse1.6.0
discourse discourse1.7.0
discourse discourse1.8.0
discourse discourse1.9.0
discourse discourse2.0.0
discourse discourse2.1.0
discourse discourse2.2.0
discourse discourse2.3.0
discourse discourse2.4.0
discourse discourse2.5.0
discourse discourse2.6.0
discourse discourse2.7.0
discourse discourse2.8.0
discourse discourse2.9.0

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
- stable: <= 3.0.2, beta: <= 3.1.0.beta3affected

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-2023-28111Mar 17, 2023 · Discourse vulnerable to SSRF protection bypass possible with IPv4-mapped IPv6 addresses
30Monitor
← EarlierCVE-2023-28112Mar 17, 2023 · Discourse's SSRF protection missing for some FastImage requests
32Monitor
Later →CVE-2023-29196Apr 18, 2023 · HTML injection via topic embedding in Discourse
24Monitor

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.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

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

No commit or PR link among the references.

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.
Administrator privileges are required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: low · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: High
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: Low

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-primary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

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

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

github.com/discourse/discourse/security/advisories/GHSA-vm65-pv5h-6g3w

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

All records