CWE-208: Observable Timing Discrepancy

How it's found

Observable Timing Discrepancy is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.

In security-relevant contexts, even small variations in timing can be exploited by attackers to indirectly infer certain details about the product's internal operations. For example, in some cryptographic algorithms, attackers can use timing differences to infer certain properties about a private key, making the key easier to guess. Timing discrepancies effectively form a timing side channel.

Vulnerable vs. safe

assign check_pass[i] = 1;continue;

assign check_pass[i] = 0;break;if (entered_pass[(i*8 - 1) : i] eq golden_pass([i*8 - 1) : i])elseendassign check_pass[3:0] = 4'b0;for (i = 0; i < 4; i++) beginassign grant_access = (check_pass == 4'b1111) ? 1'b1: 1'b0;always_comb @ (posedge clk)beginend

assign check_pass[i] = 1;continue;

assign check_pass[i] = 0;continue;if (entered_pass[(i*8 - 1) : i] eq golden_pass([i*8 -1) : i])elseendassign check_pass[3:0] = 4'b0;for (i = 0; i < 4; i++) beginassign grant_access = (check_pass == 4'b1111) ? 1'b1: 1'b0;always_comb @ (posedge clk)beginend

Consequences

• Read Application Data, Bypass Protection Mechanism

Where this fits in a TurboPentest engagement

TurboPentest's agentic pentest is powerful and covers a broad range of issues automatically. This particular class is best confirmed in a manual IntegSec engagement, where human pentesters apply deeper methodology and a larger context window than any automated pass.

Frequently asked questions

Related CWEs

• Base weakness
  CWE-203: Observable Discrepancy