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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| trailofbits | rfc3161-client | < 1.0.6 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | python-rfc3161-client | 1.0.6-1.1 | openSUSE-SU-2026:10546-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | rfc3161-client | < 1.0.6 | 1.0.6 | GHSA-3xxc-pwj6-jgrj |
Advisories 1
- openSUSE-SU-2026:10546-1 python311-rfc3161-client-1.0.6-1.1 on GA media SUSE / openSUSE Security Updates · Apr 15, 2026