CWE-203: Observable Discrepancy

The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.

Consequences

• Confidentiality, Access Control: Read Application Data, Bypass Protection Mechanism
• Confidentiality: Read Application Data

How to prevent it

• Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
• Implementation: Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success. If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.

Recent advisories

• EEF-CVE-2026-65626 — Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose
• GHSA-vwp5-f99x-x3rq — Backstage has improper input validation in scaffolder task list ordering
• GHSA-v6q3-xqxm-6f5v — Ghost: Invite Token Disclosure in Ghost Admin API
• GHSA-53vv-xm9f-mm82 — Ghost: Password Hash Ordering Disclosure in Ghost Admin API
• GHSA-2p9g-x3cv-5hh4 — Private Weblate projects vulnerable to observable object existence disclosure via globally scoped object lookups
• GHSA-8fxq-53rx-ph5f — Coder: Login endpoint user enumeration via timing-defense placeholder in password comparison
• GHSA-4pjg-x8qj-33j5 — SiYuan: authFilePublishAccess distinguishes hidden and forbidden documents from public and nonexistent ones, and issues a publish-auth cookie for documents it reports as forbidden
• GHSA-ppr4-5f46-j9c6 — Budibase: Server Filesystem Existence/Read Oracle via Builder-Controlled MongoDB tlsCertificateKeyFile
• GHSA-pgqf-926r-548m — Gitea: Cross-repository label-ID enumeration oracle via unscoped DeleteIssueLabel API
• GHSA-qhxg-623c-cfjm — NocoDB: Plaintext Password Comparison in Shared Views
• GHSA-gcg5-86jr-f7jg — Weblate Vulnerable to Private Translation Enumeration via Screenshot API
• GHSA-qpc3-fg4j-8hgm — Parse Server has a protected field change detection oracle via LiveQuery watch parameter
• GHSA-5mr9-crcg-8wh2 — Mattermost fails to use consistent error responses when handling the /mute command
• GHSA-6c9j-x93c-rw6j — OpenClaw safeBins file-existence oracle information disclosure
• GHSA-m6j8-rg6r-7mv8 — Go Ethereum Improperly Validates the ECIES Public Key in RLPx Handshake

All advisories for CWE-203