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CVE-2026-33753— Improper Certificate Validation in rfc3161-client

Quick assessment

Affected
trailofbits rfc3161-client
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

rfc3161-client是Trail of Bits开源的一个软件。 rfc3161-client 1.0.6之前版本存在安全漏洞，该漏洞源于签名验证存在授权绕过，可能导致攻击者冒充受信任的时间戳机构。

CVSS 6.2 · Medium EPSS 0.19% · P8
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I. Basic Information for CVE-2026-33753

Vulnerability Information
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Vulnerability Title
Improper Certificate Validation in rfc3161-client
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
rfc3161-client 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
rfc3161-client是Trail of Bits开源的一个软件。 rfc3161-client 1.0.6之前版本存在安全漏洞，该漏洞源于签名验证存在授权绕过，可能导致攻击者冒充受信任的时间戳机构。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

II. Public POCs for CVE-2026-33753

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III. Intelligence Information for CVE-2026-33753

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Vendor Advisories for CVE-2026-33753 (1)

IV. Related Vulnerabilities

Same product: rfc3161-client
Same vendor: trailofbits
Same weakness: CWE-295