CVE-2021-42564: An open redirect through HTML injection in confidential messages in Cryptshare before 5.1.0 allows remote atta

Q: How do I fix CVE-2021-42564?

cryptshare server: upgrade to 5.1.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-42564 being exploited?

CVE-2021-42564 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-2021-42564 affect?

CVE-2021-42564 affects cryptshare server. Severity is medium (CVSS 5.4). An open redirect through HTML injection in confidential messages in Cryptshare before 5.1.0 allows remote attackers (with permission to provide confidential messages via Cryptshare) to redirect targeted victims to any URL via the '<meta htt

Q: How urgent is CVE-2021-42564?

Priority 37/100. Public exploit reference

Routine

MEDIUM 5.4UPGRADE

CVE-2021-42564 is a medium-severity flaw (CVSS 5.4) affecting cryptshare server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An open redirect through HTML injection in confidential messages in Cryptshare before 5.1.0 allows remote attackers (with permission to provide confidential messages via Cryptshare) to redirect targeted victims to any URL via the '<meta http-equiv="refresh"' substring in the editor parameter.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-601
Published	2021-11-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: cryptshare

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

Am I affected?

Timeline

2021-11-30 20:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

cryptshare cryptshare server UPGRADE

Affected: < 5.1.0

Fixed in: 5.1.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cryptshare-server || rpm -q cryptshare-server || cryptshare-server --version

2. UPGRADE to 5.1.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cryptshare-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cryptshare-server

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-2021-42564?

cryptshare server: upgrade to 5.1.0. Exact commands for each OS are on this page.

Is CVE-2021-42564 being exploited?

CVE-2021-42564 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-2021-42564 affect?

CVE-2021-42564 affects cryptshare server. Severity is medium (CVSS 5.4). An open redirect through HTML injection in confidential messages in Cryptshare before 5.1.0 allows remote attackers (with permission to provide confidential messages via Cryptshare) to redirect targeted victims to any URL via the '<meta htt

How urgent is CVE-2021-42564?

Priority 37/100. Public exploit reference

Related CVEs

CVE-2021-3150 MEDIUM 6.1 UPGRADE A cross-site scripting (XSS) vulnerability on the Delete Personal Data page in Cryptshare Server before 4.8.0

References

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