CVE-2026-73311Network attack vector

Unauthorized token issuance via reusable authorization codes

Published Sep 8, 2026 · Updated Sep 10, 2026

OAuth2 authorization code reuse in XenForo before 2.3.13 allows remote attackers to obtain unauthorized token pairs. The token endpoint fails to invalidate or mark an authorization code as consumed after its first exchange, so replaying it issues another independent token pair. Exploitation requires a previously issued code, and each replay grants access and refresh tokens for the same user and scopes.

CVSS severity9.1
Critical
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OAuth2 authorization code reuse in XenForo before 2.3.13 allows remote attackers to obtain unauthorized token pairs. The token endpoint fails to invalidate or mark an authorization code as consumed after its first exchange, so replaying it issues another independent token pair. Exploitation requires a previously issued code, and each replay grants access and refresh tokens for the same user and scopes.

The record

CVE
CVE-2026-73311
Published
Sep 8, 2026
Updated
Sep 10, 2026
Vendor
XenForo Ltd.
Product
XenForo
Classifications
CWE-294, T1528
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record 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 <2.3.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

XenForo Ltd. · XenForoversion=0 <2.3.13

Published CVSS scores

9.1VulnCheckCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

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.

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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-294Authentication Bypass by Capture-replay
T1528Steal Application Access Token

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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