Vulnerability in rfc3161-client (CVE-2026-33753)
Summary
Vulnerability in rfc3161-client (CVE-2026-33753). Data can be tampered with by attackers. Exploitable via common_name. Mitigation: upgrade to 1.0.6 or later.
Original description
The description as published by the source.
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: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-33753 has been found in rfc3161-client.
Attackers can target a specific entry point like common_name over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 6.2/10.
What to do: upgrade rfc3161-client to 1.0.6 or later.
If unsure, ask your IT team or search "rfc3161-client CVE-2026-33753" on the vendor's site.
CVE-2026-33753 (rfc3161-client) — CWE-295 / CVSS v3 6.2
Attack vector: local / unauthenticated / no user interaction
Attack surface: common_name / SignedData / ESSCertID / ESSCertIDv2
Patched: 1.0.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-295) exists in rfc3161-client. Attackers reach the vulnerable code path via common_name without authentication.
Check the vendor advisory for the affected versions of rfc3161-client. Attack surface: common_name / SignedData / ESSCertID / ESSCertIDv2.
Severity: Medium (CVSS 6.2/10). Data can be tampered with by attackers.
Update to 1.0.6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'rfc3161-client' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'rfc3161-client' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
rfc3161-clientを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade rfc3161-client to 1.0.6ステージング環境で 1.0.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com
- web github.com