XenForo up to 2.3.12 BBCode parser recursion

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.3$0-$5k0.82+

Summaryinfo

A vulnerability was found in XenForo up to 2.3.12 and classified as problematic. Affected is an unknown function of the component BBCode parser. The manipulation results in recursion. This vulnerability is identified as CVE-2026-73321. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in XenForo up to 2.3.12. Affected is an unknown code of the component BBCode parser. The manipulation with an unknown input leads to a recursion vulnerability. CWE is classifying the issue as CWE-674. The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. This is going to have an impact on availability. CVE summarizes:

XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread.

The advisory is shared for download at xenforo.com. This vulnerability is traded as CVE-2026-73321 since 08/11/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 2.3.13 eliminates this vulnerability.

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Productinfo

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.3

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (VulnCheck): 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Recursion
CWE: CWE-674 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: XenForo 2.3.13

Timelineinfo

08/11/2026 CVE reserved
09/08/2026 +28 days Advisory disclosed
09/08/2026 +0 days VulDB entry created
09/08/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: xenforo.com
Status: Confirmed

CVE: CVE-2026-73321 (🔒)
GCVE (CVE): GCVE-0-2026-73321
GCVE (VulDB): GCVE-100-399816

Entryinfo

Created: 09/08/2026 15:39
Changes: 09/08/2026 15:39 (74)
Complete: 🔍
Cache ID: 216::103

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