CVE-2021-41868: OnionShare 2.3 before 2.4 allows remote unauthenticated attackers to upload files on a non-public node when us

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CRITICAL 9.8REMOTEUPGRADE

CVE-2021-41868 is a critical-severity flaw (CVSS 9.8) affecting onionshare. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OnionShare 2.3 before 2.4 allows remote unauthenticated attackers to upload files on a non-public node when using the --receive functionality.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Published	2021-10-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: onionshare

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

Am I affected?

Timeline

2021-10-04 14:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

onionshare onionshare UPGRADE

Affected: >= 2.3 and < 2.4

Fixed in: 2.4

Safe to downgrade to: a release before 2.3

1. Check installed version

apt-cache policy onionshare || rpm -q onionshare || onionshare --version

2. UPGRADE to 2.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade onionshare

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade onionshare

Note

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

3. If no update is available yet, DOWNGRADE to a release before 2.3 (Debian / Ubuntu)

apt-cache madison onionshare sudo apt install onionshare=<VERSION_BEFORE_2.3> sudo apt-mark hold onionshare

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list onionshare sudo dnf downgrade onionshare-<VERSION_BEFORE_2.3> sudo dnf versionlock add onionshare

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-2021-41868?

onionshare: upgrade to 2.4. Exact commands for each OS are on this page.

Is CVE-2021-41868 being exploited?

CVE-2021-41868 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-2021-41868 affect?

CVE-2021-41868 affects onionshare. Severity is critical (CVSS 9.8). OnionShare 2.3 before 2.4 allows remote unauthenticated attackers to upload files on a non-public node when using the --receive functionality.

How urgent is CVE-2021-41868?

Priority 65/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

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References

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