CVE-2026-73310: xenforo Auth Bypass — Exploit

Description

XenForo before 2.3.13 contains an authorization flaw in the OAuth2 token endpoint that allows attackers controlling any allowlisted redirect URI to bypass redirect URI binding by submitting a different allowlisted URI than the one recorded at authorization time. Attackers can exchange an intercepted authorization code using a mismatched redirect URI to steal OAuth2 tokens from intercepted authorization flows.

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CVSS v3.1 Score

5.9

MEDIUM

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

EPSS — Exploit Prediction

0.0036

Probability of exploitation

0.30%

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-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
xenforo	xenforo	< 2.3.13

References

Exploits

https://bombobombone.github.io/posts/cve-2026-73310/ https://github.com/BomboBombone/CVE-2026-73310

Other References

https://www.vulncheck.com/advisories/xenforo-oauth2-authorization-code-token-theft-via-redirect-uri-bypass 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-2026-73310? +

XenForo before 2.3.13 contains an authorization flaw in the OAuth2 token endpoint that allows attackers controlling any allowlisted redirect URI to bypass redirect URI binding by submitting a different allowlisted URI than the one recorded at authorization time. Attackers can exchange an intercepted authorization code using a mismatched redirect URI to steal OAuth2 tokens from intercepted authorization flows. It has a CVSS v3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2026-73310? +

CVE-2026-73310 has a CVSS v3.1 score of 5.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0036, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-73310? +

CVE-2026-73310 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-2026-73310? +

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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