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No exploitation reportedFix available

CVE-2021-32749

No exploitation reported by the sources we read.

  • Published2021-07-16
  • Fixed in0.11.3 · 0.10.7
  • WeaknessCWE-78 · CWE-94

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

fail2ban is a daemon to ban hosts that cause multiple authentication errors. In versions 0.9.7 and prior, 0.10.0 through 0.10.6, and 0.11.0 through 0.11.2, there is a vulnerability that leads to possible remote code execution in the mailing action mail-whois. Command `mail` from mailutils package used in mail actions like `mail-whois` can execute command if unescaped sequences (`\n~`) are available in "foreign" input (for instance in whois output). To exploit the vulnerability, an attacker would need to insert malicious characters into the response sent by the whois server, either via a MITM attack or by taking over a whois server. The issue is patched in versions 0.10.7 and 0.11.3. As a workaround, one may avoid the usage of action `mail-whois` or patch the vulnerability manually.

Timeline

dates in UTC
  1. 2021-07-1618:15CVE publishedNVD

Versions per branch

NVD
Fail2ban
BranchAffectedFixed in
0.11≥ 0.11.0, < 0.11.30.11.3
0.10≥ 0.10.0, < 0.10.70.10.7
0.9≤ 0.9.7no fix published
Fedoraproject fedora
BranchAffectedFixed in
34.x= 34no fix published
35.x= 35no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • fail2banUbuntu:Pro:20.04:LTSall versions · fixed in 0.11.1-1ubuntu0.1~esm1
  • fail2banUbuntu:Pro:18.04:LTSall versions · fixed in 0.10.2-2ubuntu0.1~esm1
  • fail2banUbuntu:Pro:16.04:LTSall versions · fixed in 0.9.3-1ubuntu0.1~esm1
  • fail2banUbuntu:Pro:14.04:LTSall versions · fixed in 0.8.11-1ubuntu0.1~esm1
  • fail2banSUSE:Package Hub 15 SP3all versions · fixed in 0.11.2-bp153.2.3.1
  • fail2banSUSE:Package Hub 15 SP2all versions · fixed in 0.11.2-bp153.2.3.1
  • fail2banSUSE:Package Hub 15 SP1all versions · fixed in 0.11.2-bp153.2.3.1
  • fail2banopenSUSE:Tumbleweedall versions · fixed in 0.11.2-3.1

17 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-32749 Red Hat Product Security

    fail2ban: Command injection via mail comand

Full record on NVD

Fix

  1. Update Fail2ban to 0.11.3 · 0.10.7

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CNACVSS 3.16.1known since 2026-10-23
  • NVDCVSS 3.18.1read 2026-10-23
  • NVDCVSS 2.06.8read 2026-10-23
  • CNAweakness (CWE)CWE-78known since 2026-10-23
  • NVDweakness (CWE)CWE-94read 2026-10-23
  • FIRST EPSSEPSS score3.4 %2026-11-09
  • OSVaffected packages—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-07-16
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-32749?

fail2ban is a daemon to ban hosts that cause multiple authentication errors. In versions 0.9.7 and prior, 0.10.0 through 0.10.6, and 0.11.0 through 0.11.2, there is a vulnerability that leads to possible remote code execution in the mailing action mail-whois. Command `mail` from mailutils package used in mail actions like `mail-whois` can execute command if unescaped sequences (`\n~`) are available in "foreign" input (for instance in whois output). To exploit the vulnerability, an attacker would need to insert malicious characters into the response sent by the whois server, either via a MITM attack or by taking over a whois server. The issue is patched in versions 0.10.7 and 0.11.3. As a workaround, one may avoid the usage of action `mail-whois` or patch the vulnerability manually.

Is CVE-2021-32749 actively exploited?

Active exploitation of CVE-2021-32749 has not been confirmed. Its EPSS score was 3.4% on 2026-11-09, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-32749?

CVE-2021-32749 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

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