CVE-2021-29435: trestle-auth is an authentication plugin for the Trestle admin framework

This month

HIGH 8.1DOWNGRADE

CVE-2021-29435 is a high-severity flaw (CVSS 8.1) affecting trestle-auth. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

trestle-auth is an authentication plugin for the Trestle admin framework. A vulnerability in trestle-auth versions 0.4.0 and 0.4.1 allows an attacker to create a form that will bypass Rails' built-in CSRF protection when submitted by a victim with a trestle-auth admin session. This potentially allows an attacker to alter protected data, including admin account credentials. The vulnerability has been fixed in trestle-auth 0.4.2 released to RubyGem

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.7% (top 48%)
CISA exploited list	No
Weakness	CWE-352
Published	2021-04-13
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: trestle-auth project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-04-13 20:15 UTCPublished CVE record published
2026-06-17 03:47 UTCUpdated Record last modified

trestle-auth project trestle-auth DOWNGRADE

Affected: 0.4.0 · 0.4.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.4.0

1. Check installed version

apt-cache policy trestle-auth || rpm -q trestle-auth || trestle-auth --version

2. No fixed release: DOWNGRADE to a release before 0.4.0 (Debian / Ubuntu)

apt-cache madison trestle-auth sudo apt install trestle-auth=<VERSION_BEFORE_0.4.0> sudo apt-mark hold trestle-auth

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list trestle-auth sudo dnf downgrade trestle-auth-<VERSION_BEFORE_0.4.0> sudo dnf versionlock add trestle-auth

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2021-29435?

trestle-auth: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-29435 being exploited?

CVE-2021-29435 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-2021-29435 affect?

CVE-2021-29435 affects trestle-auth. Severity is high (CVSS 8.1). trestle-auth is an authentication plugin for the Trestle admin framework. A vulnerability in trestle-auth versions 0.4.0 and 0.4.1 allows an attacker to create a form that will bypass Rails' built-in CSRF protection when submitted by a vict

How urgent is CVE-2021-29435?

Priority 41/100. High severity

Software pages

Ruby on Rails vulnerabilities

References

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