CVE-2026-33753: rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161

Q: How do I fix CVE-2026-33753?

rfc3161-client: upgrade to 1.0.6. Exact commands for each OS are on this page.

Q: Is CVE-2026-33753 being exploited?

CVE-2026-33753 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-33753 affect?

CVE-2026-33753 affects rfc3161-client. Severity is medium (CVSS 6.2). 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 trust

Q: How urgent is CVE-2026-33753?

Priority 29/100. Public exploit reference

Routine

MEDIUM 6.2UPGRADE

CVE-2026-33753 is a medium-severity flaw (CVSS 6.2) affecting rfc3161-client. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 t

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.2 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 92%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-04-08
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: trailofbits

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-08 16:16 UTCPublished CVE record published
2026-07-24 23:10 UTCUpdated Record last modified

trailofbits rfc3161-client UPGRADE

Affected: < 1.0.6

Fixed in: 1.0.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy rfc3161-client || rpm -q rfc3161-client || rfc3161-client --version

2. UPGRADE to 1.0.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade rfc3161-client

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade rfc3161-client

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-33753?

rfc3161-client: upgrade to 1.0.6. Exact commands for each OS are on this page.

Is CVE-2026-33753 being exploited?

CVE-2026-33753 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33753 affect?

CVE-2026-33753 affects rfc3161-client. Severity is medium (CVSS 6.2). 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 trust

How urgent is CVE-2026-33753?

Priority 29/100. Public exploit reference

Software pages

Python vulnerabilities

References

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