CVE-2021-44138: There is a Directory traversal vulnerability in Caucho Resin, as distributed in Resin 4.0.52 - 4.0.56, which a

Q: How do I fix CVE-2021-44138?

resin: upgrade to newer than 4.0.56. Exact commands for each OS are on this page.

Q: Is CVE-2021-44138 being exploited?

CVE-2021-44138 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-2021-44138 affect?

CVE-2021-44138 affects resin. Severity is high (CVSS 7.5). There is a Directory traversal vulnerability in Caucho Resin, as distributed in Resin 4.0.52 - 4.0.56, which allows remote attackers to read files in arbitrary directories via a ; in a pathname within an HTTP request.

Q: How urgent is CVE-2021-44138?

Priority 60/100. High severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2021-44138 is a high-severity flaw (CVSS 7.5) affecting resin. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

There is a Directory traversal vulnerability in Caucho Resin, as distributed in Resin 4.0.52 - 4.0.56, which allows remote attackers to read files in arbitrary directories via a ; in a pathname within an HTTP request.

Why this priority

High severity
EPSS top 4%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	12.3% (top 4%)
CISA exploited list	No
Weakness	CWE-22
Published	2022-04-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: caucho

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

Am I affected?

Timeline

2022-04-04 13:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

caucho resin UPGRADE

Affected: >= 4.0.52 and <= 4.0.56

Fixed in: newer than 4.0.56

Safe to downgrade to: a release before 4.0.52

1. Check installed version

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

2. UPGRADE to newer than 4.0.56 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade resin

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 4.0.52 (Debian / Ubuntu)

apt-cache madison resin sudo apt install resin=<VERSION_BEFORE_4.0.52> sudo apt-mark hold resin

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

dnf --showduplicates list resin sudo dnf downgrade resin-<VERSION_BEFORE_4.0.52> sudo dnf versionlock add resin

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: Caucho Resin >=4.0.52 <=4.0.56 - Directory traversal

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-2021-44138?

resin: upgrade to newer than 4.0.56. Exact commands for each OS are on this page.

Is CVE-2021-44138 being exploited?

CVE-2021-44138 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-2021-44138 affect?

CVE-2021-44138 affects resin. Severity is high (CVSS 7.5). There is a Directory traversal vulnerability in Caucho Resin, as distributed in Resin 4.0.52 - 4.0.56, which allows remote attackers to read files in arbitrary directories via a ; in a pathname within an HTTP request.

How urgent is CVE-2021-44138?

Priority 60/100. High severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

References

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