CVE-2024-53851 [Medium] | Denial of Service in Discourse

Discourse is an open source platform for community discussion. In affected versions the endpoint for generating inline oneboxes for URLs wasn't enforcing limits on the number of URLs that it accepted, allowing a malicious user to inflict denial of service on some parts of the app. This vulnerability is only exploitable by authenticated users. This issue has been patched in the latest stable, beta and tests-passed versions of Discourse. Users are advised to upgrade. Users unable to upgrade should turn off the `enable inline onebox on all domains` site setting and remove all entries from the `allowed inline onebox domains` site setting.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-03-16	0.11%	0.18%	+0.08%
2	2026-03-15	0.32%	0.11%	-0.21%
3	2025-12-28	—	0.32%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-03-16

0.11%

0.18%

+0.08%

2026-03-15

0.32%

0.11%

-0.21%

2025-12-28

—

0.32%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
4.3	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	2.8	1.4	[email protected]
6.5	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

4.3

3.1

MEDIUM

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

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

2.8

1.4

[email protected]

6.5

3.1

MEDIUM

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

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.8

3.6

[email protected]

Affected software / configurations for CVE-2024-53851

Vendor	Product	Version	Raw CPE
discourse	discourse	< 3.3.3	cpe:2.3:a:discourse:discourse:::::stable:::*
discourse	discourse	< 3.4.0	cpe:2.3:a:discourse:discourse:::::beta:::*
discourse	discourse	3.4.0	cpe:2.3:a:discourse:discourse:3.4.0:beta1:::beta:::*
discourse	discourse	3.4.0	cpe:2.3:a:discourse:discourse:3.4.0:beta2:::beta:::*
discourse	discourse	3.4.0	cpe:2.3:a:discourse:discourse:3.4.0:beta3:::beta:::*

References for CVE-2024-53851

URL	Tags
https://github.com/discourse/discourse/commit/416ec83ae57924d721e6e374f4cda78bd77a4599	Patch
https://github.com/discourse/discourse/security/advisories/GHSA-49rv-574x-wgpc	Third Party Advisory

URL

CVE-2024-53851 | Partial denial of service via inline oneboxes in Discourse

Exploit prediction scoring system (EPSS) score for CVE-2024-53851

Common vulnerability scoring system (CVSS) metrics for CVE-2024-53851

Weakness enumeration for CVE-2024-53851

Affected software / configurations for CVE-2024-53851

References for CVE-2024-53851