CVE-2021-31800: Multiple path traversal vulnerabilities exist in smbserver.py in Impacket through 0.9.22

Q: How do I fix CVE-2021-31800?

impacket: upgrade to newer than 0.9.22; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-31800 being exploited?

CVE-2021-31800 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-2021-31800 affect?

CVE-2021-31800 affects impacket, fedora. Severity is critical (CVSS 9.8). Multiple path traversal vulnerabilities exist in smbserver.py in Impacket through 0.9.22. An attacker that connects to a running smbserver instance can list and write to arbitrary files via ../ directory traversal. This could potentially be

Q: How urgent is CVE-2021-31800?

Priority 64/100. Critical severity; EPSS top 3%: very likely to be exploited; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADEMITIGATE

CVE-2021-31800 is a critical-severity flaw (CVSS 9.8) affecting impacket, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Multiple path traversal vulnerabilities exist in smbserver.py in Impacket through 0.9.22. An attacker that connects to a running smbserver instance can list and write to arbitrary files via ../ directory traversal. This could potentially be abused to achieve arbitrary code execution by replacing /etc/shadow or an SSH authorized key.

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
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	19.4% (top 3%)
CISA exploited list	No
Weakness	CWE-22
Published	2021-05-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · secureauth

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

Am I affected?

Timeline

2021-05-05 11:15 UTCPublished CVE record published
2026-06-17 03:52 UTCUpdated Record last modified

secureauth impacket UPGRADE

Affected: <= 0.9.22

Fixed in: newer than 0.9.22

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 0.9.22 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade impacket

Note

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

fedoraproject fedora MITIGATE

Affected: 32 · 33 · 34

Fixed in: no fixed release known

Safe to downgrade to: a release before 32

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2021-31800?

impacket: upgrade to newer than 0.9.22; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-31800 being exploited?

CVE-2021-31800 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-2021-31800 affect?

CVE-2021-31800 affects impacket, fedora. Severity is critical (CVSS 9.8). Multiple path traversal vulnerabilities exist in smbserver.py in Impacket through 0.9.22. An attacker that connects to a running smbserver instance can list and write to arbitrary files via ../ directory traversal. This could potentially be

How urgent is CVE-2021-31800?

Priority 64/100. Critical severity; EPSS top 3%: very likely to be exploited; Remotely exploitable, no login, no user action

References

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