CWE-205
Observable Behavioral Discrepancy
Extended description
Ideally, a product should provide as little information about its internal operations as possible. Otherwise, attackers could use knowledge of these internal operations to simplify or optimize their attack. In some cases, behavioral discrepancies can be used by attackers to form a side channel.
Common consequences1
- ConfidentialityAccess ControlRead Application DataBypass Protection Mechanism
CVEs referencing this CWE3
| CVE | Description | Severity | EPSS | Flags | Modified |
|---|---|---|---|---|---|
| CVE-2017-11155 | An information exposure vulnerability in index.php in Synology Photo Station before 6.7.3-3432 and 6.3-2967 allows remote attackers to obtain sensitive system information via unspecified vectors. | NONE | 47%p99 | Functional | 2026-06-17 |
| CVE-2024-6129 | A vulnerability, which was classified as problematic, was found in spa-cartcms 1.9.0.6. Affected is an unknown function of the file /login of the component Username Handler. The manipulation of the argument email leads to observable behavioral discrepancy. It is possible to launch the attack remotely. The complexity of an attack is rather high. The exploitability is told to be difficult. The exploit has been disclosed to the public and may be used. The identifier of this vulnerability is VDB-268896. | LOW3.7 | 0.61%p49 | 2026-06-17 | |
| CVE-2026-109125 | In NLnet Labs Unbound up to and including version 1.26.1, an observable cache-level side-channel can be exposed with 'unwanted-reply-threshold > 0' configurations (not a default configuration). If a response-like UDP datagram reaches the upstream source port currently used by a recursive query, but its TXID does not match any pending query, Unbound counts the packet as an unwanted reply. When the accumulated count reaches the configured threshold, Unbound clears the worker's RRset cache and message cache. This cache clear action does not destroy the current upstream UDP pending query. Therefore, an external observer can distinguish whether a candidate port matches the current upstream source port by checking whether an existing cached item has been cleared. This is a cache side-channel vulnerability that can be used to probe the upstream source port. Although the attack is not feasible on default configurations and the suggested value (10 million) makes it an ureliable attack on a public resolver, in scenarios where the attacker can keep a concurrent query window alive, the attacker can first filter the source port and then perform birthday-style guessing against the TXID, making cache poisoning a feasible attack path. | MEDIUM5.3 | 0.17%p7 | 2026-10-22 |