NVD / CVE Program· CNA GitHub_M

CVE-2021-32749: Possible RCE vulnerability in mailing action using mailutils (mail-whois)

Noroxi assessment

Priority: Monitor (action score 33/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 3.4% (FIRST EPSS); higher than 89% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
Fixed version: fail2ban (Alpine:v3.15) 0.11.2-r1; fail2ban (Alpine:v3.16) 0.11.2-r2; fail2ban (Debian:12) 0.11.2-2.
Severity is disputed: the assigning authority (CNA) scores it 6.1, NVD 8.1.

Low priority for now. Upgrade to fail2ban (Alpine:v3.15) 0.11.2-r1; fail2ban (Alpine:v3.16) 0.11.2-r2; fail2ban (Debian:12) 0.11.2-2 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 8.1 · v3.1—No exploit Fix available

Published: Jul 16, 2021
Updated: Jun 16, 2026
EPSS: 3.4% · 89th percentile
CWE: CWE-78

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 32 / 40 · 8.1 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 3.4%

CNA vs NVD score

NVD: 8.1
CNA · GitHub_M: 6.1; 2.0 point gap

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
fail2ban	fail2ban	cpe:2.3:a:fail2ban:fail2ban
fedoraproject	fedora	cpe:2.3:o:fedoraproject:fedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

fail2ban fail2banup to 0.9.7 inclusive
fail2ban fail2ban0.10.0 and later · before 0.10.7
fail2ban fail2ban0.11.0 and later · before 0.11.3
fedoraproject fedora34
fedoraproject fedora35

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

fail2ban fail2ban
- <= 0.9.7, >= 0.10.0, <= 0.10.6, >= 0.11.0, <= 0.11.2affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.15	fail2ban	from 0.10.0 · before 0.11.2-r1	0.11.2-r1
Alpine:v3.16	fail2ban	from 0.10.0 · before 0.11.2-r2	0.11.2-r2
Debian:12	fail2ban	before 0.11.2-2	0.11.2-2
openSUSE:Leap 15.2	fail2ban	before 0.11.2-bp153.2.3.1	0.11.2-bp153.2.3.1
openSUSE:Tumbleweed	fail2ban	before 0.11.2-3.1	0.11.2-3.1
SUSE:Package Hub 15 SP1	fail2ban	before 0.11.2-bp153.2.3.1	0.11.2-bp153.2.3.1

Same product

fail2ban: all records

Other highest-scoring records for the same primary product.

CVE-2012-5642server/action.py in Fail2ban before 0.8.8 does not properly handle the content of the matches tag, which might allow remote attackers to tri
31Monitor
CVE-2007-4321fail2ban 0.8 and earlier does not properly parse sshd log files, which allows remote attackers to add arbitrary hosts to the /etc/hosts.deny
29Monitor
CVE-2026-109786In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf) accepts an "on <token>" suffix after the host a
21Monitor

Published before and after this one in the same product

← EarlierCVE-2013-7176Feb 1, 2014 · config/filter.d/postfix.conf in the postfix filter in Fail2ban before 0.8.11 allows remote attackers to trigger the blocking of an arbitrary
21Monitor
← EarlierCVE-2013-7177Feb 1, 2014 · config/filter.d/cyrus-imap.conf in the cyrus-imap filter in Fail2ban before 0.8.11 allows remote attackers to trigger the blocking of an arb
21Monitor
← EarlierCVE-2009-5023Jun 10, 2014 · The (1) dshield.conf, (2) mail-buffered.conf, (3) mynetwatchman.conf, and (4) mynetwatchman.conf actions in action.d/ in Fail2ban before 0.8
18Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
alpine:fail2ban	0.11.2-r1 · Alpine:v3.15	Package registry (OSV)
debian:fail2ban	0.11.2-2 · Debian:12	Package registry (OSV)
opensuse:fail2ban	0.11.2-bp153.2.3.1 · openSUSE:Leap 15.2	Package registry (OSV)
suse:fail2ban	0.11.2-bp153.2.3.1 · SUSE:Package Hub 15 SP1	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-78 · Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Root cause

User input is inserted as text into a shell command. The shell may interpret special characters in the input as part of the command.

The bug in code

The whole CWE-78 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const host = req.body.host;
2exec("ping -c 1 " + host, onResult);

Fixed

1const host = req.body.host;
2if (!/^[a-z0-9.-]{1,253}$/i.test(host)) return res.sendStatus(400);
3execFile("ping", ["-c", "1", host], onResult);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

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References

github.com/fail2ban/fail2ban/commit/2ed414ed09b3bb4c478abc9366a1ff22024a33c9

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records