fail2ban — security advisory
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.
- Products
- fail2ban
- Affected versions
- Not specified
- Fixed versions
- 0.11.2-2
- CVEs
- CVE-2021-32749
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 00:10 UTC · Revision 1
Source evidence
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.
osv:DEBIAN-CVE-2021-32749
fail2ban
Fixed versions: 0.11.2-2
fail2ban
Fixed versions: 0.11.2-2
fail2ban
Fixed versions: 0.11.2-2
Complete source record
{
"id": "31270e9319adad3e1fa913a9f00ab3c419803e2e5aefeec1c92801fe1e2c10a8",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2021-32749",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2021-32749",
"summary": "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.",
"evidence": "osv:DEBIAN-CVE-2021-32749",
"products": [
{
"name": {
"value": "fail2ban",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "0.11.2-2",
"evidence": "/affected/0/ranges"
}
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"affected_versions": []
},
{
"name": {
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"evidence": "/affected/1/ranges"
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{
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"severity": "high",
"structured": {
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"aliases": [
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"metrics": [
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"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
}
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"affected": [
{
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"package": {
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"purl": "pkg:deb/debian/fail2ban?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-32749.json"
},
"ecosystem_specific": {
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}
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{
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"package": {
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"purl": "pkg:deb/debian/fail2ban?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-32749.json"
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"package": {
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"purl": "pkg:deb/debian/fail2ban?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-32749.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-23T18:03:03.070868426Z",
"provider": "osv",
"upstream": [
"CVE-2021-32749"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2021-32749"
]
},
"related_cves": [
{
"value": "CVE-2021-32749",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 420223,
"published_at": "2021-07-16T18:15:08.27+00:00"
}