CVE-2026-73311: xenforo — Exploit

Description

XenForo before 2.3.13 contains an OAuth2 authorization code reuse vulnerability that allows attackers to obtain unauthorized token pairs by submitting a previously used authorization code. Attackers can exploit the failure to invalidate or mark authorization codes as consumed after initial token issuance to receive an independent token pair for the same user and scopes, bypassing the single-use guarantee of the OAuth2 authorization code flow.

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CVSS v3.1 Score

7.4

HIGH

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

EPSS — Exploit Prediction

0.0050

Probability of exploitation

0.41%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-294 CWE-294

Affected Products

Vendor	Product	Versions
xenforo	xenforo	< 2.3.13

References

Exploits

https://bombobombone.github.io/posts/cve-2026-73311/ https://github.com/BomboBombone/CVE-2026-73311

Other References

https://www.vulncheck.com/advisories/xenforo-oauth2-authorization-code-reuse https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/ https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/

Frequently Asked Questions

What is CVE-2026-73311? +

XenForo before 2.3.13 contains an OAuth2 authorization code reuse vulnerability that allows attackers to obtain unauthorized token pairs by submitting a previously used authorization code. Attackers can exploit the failure to invalidate or mark authorization codes as consumed after initial token issuance to receive an independent token pair for the same user and scopes, bypassing the single-use guarantee of the OAuth2 authorization code flow. It has a CVSS v3.1 base score of 7.4 (HIGH).

How severe is CVE-2026-73311? +

CVE-2026-73311 has a CVSS v3.1 score of 7.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0050, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-73311? +

CVE-2026-73311 affects products from xenforo, specifically: xenforo. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-73311? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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