CVE-2024-27899: NetWeaver AS Java Auth Bypass Flaw

CVE-2024-27899 Overview

CVE-2024-27899 affects the Self-Registration and Modify Profile features in the User Admin Application of SAP NetWeaver Application Server (AS) Java. The application does not enforce proper security requirements on the content of newly defined security answers. An attacker can leverage this weakness to compromise account recovery flows that depend on security questions.

The vulnerability is categorized under CWE-640: Weak Password Recovery Mechanism for Forgotten Password. Successful exploitation produces a high impact on confidentiality and a low impact on integrity and availability. The flaw is network-reachable and requires user interaction during the attack chain.

Critical Impact
Attackers can abuse weak security-answer enforcement in NetWeaver AS Java to subvert password recovery, leading to account takeover and exposure of sensitive user data.

Affected Products

SAP NetWeaver Application Server Java (User Admin Application)
Self-Registration component of NetWeaver AS Java
Modify Profile component of NetWeaver AS Java

Discovery Timeline

2024-04-09 - CVE-2024-27899 published to NVD alongside SAP Security Patch Day disclosures
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2024-27899

Vulnerability Analysis

The User Admin Application in SAP NetWeaver AS Java exposes Self-Registration and Modify Profile workflows that allow end users to set or change their security question and answer. These answers are subsequently used to validate identity during account recovery operations. The application accepts security answers without enforcing the content controls expected for a credential-equivalent value.

Because the security answer functions as an authentication factor for recovery flows, weak content validation reduces the effective entropy of that factor. An attacker who can guess or enumerate predictable answers gains the ability to reset another user's credentials. The Common Vulnerability Scoring System (CVSS) vector indicates the impact crosses a security scope boundary, reflecting that compromise of the answer translates into broader account compromise.

Root Cause

The root cause is missing or insufficient validation logic on the security-answer input field during self-registration and profile modification. The application does not enforce constraints such as minimum complexity, prohibited values, or uniqueness checks against weak or predictable strings. This matches the [CWE-640] pattern where the recovery mechanism itself becomes the weakest link in the authentication chain.

Attack Vector

An unauthenticated attacker reaches the vulnerable endpoints over the network. The attack requires user interaction, typically tricking the victim into setting a trivially guessable security answer or exploiting accounts where weak answers were already accepted. Once the attacker submits or guesses the weak answer through the recovery workflow, they reset the victim's credentials and assume the account identity. From there, attackers pivot into the NetWeaver AS Java application context with the victim's privileges.

The vulnerability is described in prose only. Refer to SAP Note #3434839 for vendor-specific technical details.

Detection Methods for CVE-2024-27899

Indicators of Compromise

Unexpected password reset events on NetWeaver AS Java user accounts initiated through the User Admin self-service flows.
Repeated failed security-answer attempts followed by a successful reset for the same user identifier.
Profile modifications setting trivial security answers (single character, common words, repeated patterns).

Detection Strategies

Audit UME (User Management Engine) logs for password recovery and security-answer change events with abnormal frequency or off-hours timing.
Correlate self-registration events with subsequent privileged actions performed by the new account.
Flag accounts whose stored security answers match a curated list of weak or common values during periodic credential hygiene reviews.

Monitoring Recommendations

Forward NetWeaver AS Java security audit logs to a centralized SIEM for retention and correlation.
Alert on bursts of recovery requests originating from a single IP or targeting multiple distinct usernames.
Track changes to the User Admin Application configuration that relax security-answer policy enforcement.

How to Mitigate CVE-2024-27899

Immediate Actions Required

Apply the SAP patch referenced in SAP Note #3434839 to all NetWeaver AS Java instances exposing the User Admin Application.
Disable Self-Registration on internet-facing NetWeaver AS Java systems if it is not required for business operations.
Force a reset of stored security answers for users who configured them before the patch was applied.

Patch Information

SAP released the fix as part of the April 2024 Security Patch Day. Customers must download and apply SAP Note #3434839 and review the SAP Security Note News for related guidance. The patch enforces stronger content requirements on security answers submitted through Self-Registration and Modify Profile.

Workarounds

Restrict network exposure of the User Admin Application to trusted internal networks using a web application firewall or reverse proxy ACL.
Replace security-question based recovery with administrator-driven password reset workflows until the patch is deployed.
Enforce multi-factor authentication on accounts that retain access to the NetWeaver AS Java User Admin interface.

bash

# Reference: consult SAP Note #3434839 for exact parameter names
# Example concept - disable self-registration via UME property
# ume.logon.selfreg=FALSE
# ume.logon.selfreg_anonymous=FALSE