SecuriTricks - CVE-2026-33753

Description

rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates, an attacker can append a spoofed certificate matching the target common_name and Extended Key Usage (EKU) requirements. This tricks the library into verifying these authorization rules against the forged certificate while validating the cryptographic signature against an actual trusted TSA (such as FreeTSA), thereby bypassing the intended TSA authorization pinning entirely. This vulnerability is fixed in 1.0.6.

Product(s) Impacted

Vendor	Product	Versions
Python	Rfc3161-client	<1.0.6

Weaknesses

Common security weaknesses mapped to this vulnerability.

CWE-295

Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate.

*CPE(s)

Affected systems and software identified for this CVE.

Type	Vendor	Product	Version	Update	Edition	Language	Software Edition	Target Software	Target Hardware	Other Information
a	python	rfc3161-client	<1.0.6	/	/	/	/	/	/	/

References

https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj

CVSS Score

6.2 / 10

CVSS Data - 3.1

Attack Vector: LOCAL
Attack Complexity: LOW
Privileges Required: NONE
Scope: UNCHANGED
Confidentiality Impact: NONE
Integrity Impact: HIGH
Availability Impact: NONE

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

View Vector String

Timeline

Published: April 8, 2026, 4:16 p.m.
Last Modified: April 8, 2026, 9:26 p.m.

Status : Awaiting Analysis

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

[email protected]

CVE-2026-33753