CVE-2026-49265
Description
A flaw was found in oauthlib. A timing side-channel vulnerability in the Proof Key for Code Exchange (PKCE) validation process allows a remote attacker to recover secret verification codes. Because comparison operations do not execute in constant time, an attacker who has intercepted an authorization code can measure response latency differences across repeated requests to infer the expected verification code character-by-character. Successful exploitation allows the attacker to exchange the authorization code for an access token and impersonate the victim user.
Statement
This vulnerability is rated as having a Moderate impact because successful exploitation requires multiple stringent prerequisites, including intercepting a valid authorization code, measuring high-resolution network response times, and an OAuth server implementation that permits repeated verification attempts without revoking the code. While oauthlib facilitates PKCE validation in OAuth 2.0 deployments across Red Hat environments, the timing discrepancies are minor and highly susceptible to network noise in real-world scenarios. Consequently, extracting secret verifiers remotely presents significant practical hurdles.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.8 | N/A | 6.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Confidentiality,Access Control
Technical Impact: Read Application Data; Bypass Protection Mechanism
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.
Frequently Asked Questions
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