CVE-2026-33753
Description
A flaw was found in rfc3161-client, a Python library implementing the Time-Stamp Protocol (TSP). This authorization bypass vulnerability allows a remote attacker to impersonate a trusted TimeStamping Authority (TSA). The flaw exists in the library's signature verification process, specifically in how it extracts certificates from a PKCS#7 bag (a standard for cryptographic messages). An attacker can exploit a logic error to present a forged certificate, leading the library to incorrectly validate authorization rules and bypass intended TSA authorization pinning.
Statement
This vulnerability has a Moderate impact. A flaw in the rfc3161-client library, used by Red Hat Trusted Artifact Signer, allows an attacker to bypass authorization and impersonate a trusted TimeStamping Authority. This is due to a logic error in how the library extracts certificates during signature verification, enabling the use of a forged certificate to bypass TSA authorization pinning. As a consequence of a successful attack applications relying in rfc3161-client to validate the origin of a timestamp are exposed to impersonation, causing a high impact in the integrity of the data related to the validation.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.2 | 7.5 | 6.2 |
| Attack Vector | Local | Network | Local |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | High | High | High |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Authentication
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
Frequently Asked Questions
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