CVE-2023-47120Network attack vector

Service interruption via cached oversized favicon URLs

Published Nov 10, 2023 · Updated Sep 3, 2024

Resource exhaustion in Discourse 3.1.0 through 3.1.2 allows remote attackers to interrupt service through Onebox previews. Onebox's standard embed code accepts an abnormally long favicon href from attacker-controlled HTML and repeatedly caches it in Redis without a tight URL-length limit. The same flaw affects beta and tests-passed 3.1.0.beta6 through 3.2.0.beta2; repeated previews can deplete Redis and make the forum unavailable without exposing or altering forum data.

CVSS severity7.5
High
EPSS probability0.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Discourse 3.1.0 through 3.1.2 allows remote attackers to interrupt service through Onebox previews. Onebox's standard embed code accepts an abnormally long favicon href from attacker-controlled HTML and repeatedly caches it in Redis without a tight URL-length limit. The same flaw affects beta and tests-passed 3.1.0.beta6 through 3.2.0.beta2; repeated previews can deplete Redis and make the forum unavailable without exposing or altering forum data.

The record

CVE
CVE-2023-47120
Published
Nov 10, 2023
Updated
Sep 3, 2024
Vendor
Discourse
Product
Discourse
Classifications
CWE-770, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.1.3
  2. Affected versionversion=>= 3.1.0, < 3.1.3
  3. Affected versionversion=>= 3.1.0.beta6, < 3.2.0.beta3
  4. Affected versionversion=3.1.0.beta6 <3.2.0.beta3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Discourse · Discourseversion=0 <3.1.3; version=>= 3.1.0, < 3.1.3; version=>= 3.1.0.beta6, < 3.2.0.beta3; version=3.1.0.beta6 <3.2.0.beta3

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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