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CVE-2026-28812 – Privilege Escalation via User Impersonation – Apache JSPWiki up to 2.12.3

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Summary

CVE-2026-28812 is a critical privilege escalation vulnerability in Apache JSPWiki affecting all versions up to and including 2.12.3. The flaw resides in the UserManager component, which fails to sanity-check the user database at application startup — classified as CWE-290 (Authentication Bypass by Spoofing) — enabling unauthenticated network attackers to impersonate legitimate users and escalate their privileges. The vulnerability carries a CVSS v3.1 base score of 9.8 (Critical) and requires no credentials or user interaction to exploit.

Technical details

  • Root cause: The UserManager component does not validate the integrity of the user database during application initialization, leaving stored user entries and their associated permissions unchecked (CWE-290: Authentication Bypass by Spoofing).
  • Trigger conditions: An unauthenticated remote attacker can exploit the absent validation logic to manipulate user identity, assuming the role of an existing user — including privileged accounts.
  • Attack vector: Fully network-accessible; no credentials required, no user interaction needed (AV:N / AC:L / PR:N / UI:N).
  • Impact: Successful exploitation enables full user impersonation and privilege escalation, with high impact to confidentiality, integrity, and availability of the affected JSPWiki instance — including potential access to all wiki content and administrative functions.

Affected software

  • Apache JSPWiki versions up to and including 2.12.3

Severity

CVSS v3.1 Base Score: 9.8 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade to Apache JSPWiki version 2.12.4 or later, which contains the vendor-provided fix.
  • If immediate patching is not feasible, restrict network-level access to JSPWiki deployments and limit exposure to trusted internal networks only until the upgrade can be applied.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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