How severe is CVE-2021-36386?

CVE-2021-36386 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-36386 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-36386?

CVE-2021-36386 primarily affects Fetchmail. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-36386?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-36386 published?

CVE-2021-36386 was published on 2021-07-30 and last updated on 2026-06-17.

CVE-2021-36386

CVE-2021-36386 is a high-severity vulnerability in Fetchmail with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-909.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-909
Affected product: Fetchmail
Published: 2021-07-30
Last modified: 2026-06-17

Description

report_vbuild in report.c in Fetchmail before 6.4.20 sometimes omits initialization of the vsnprintf va_list argument, which might allow mail servers to cause a denial of service or possibly have unspecified other impact via long error messages. NOTE: it is unclear whether use of Fetchmail on any realistic platform results in an impact beyond an inconvenience to the client user.

Frequently asked questions

What is CVE-2021-36386?: report_vbuild in report.c in Fetchmail before 6.4.20 sometimes omits initialization of the vsnprintf va_list argument, which might allow mail servers to cause a denial of service or possibly have unspecified other impact via long error messages. NOTE: it is unclear whether use of Fetchmail on any realistic platform results in an impact beyond an inconvenience to the client user.
How severe is CVE-2021-36386?: CVE-2021-36386 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-36386 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-36386?: CVE-2021-36386 primarily affects Fetchmail. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-36386?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-36386 published?: CVE-2021-36386 was published on 2021-07-30 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:fetchmail:fetchmail:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

More vulnerabilities in Fetchmail

CVE-2001-1009 — Critical (CVSS 10.0): Fetchmail (aka fetchmail-ssl) before 5.8.17 allows a remote malicious (1) IMAP server or (2) POP/POP3 server to…
CVE-2001-0101 — Critical (CVSS 10.0): Vulnerability in fetchmail 5.5.0-2 and earlier in the AUTHENTICATE GSSAPI command.
CVE-2006-5974 — High (CVSS 7.8): fetchmail 6.3.5 and 6.3.6 before 6.3.6-rc4, when refusing a message delivered via the mda option, allows remote…
CVE-2006-5867 — High (CVSS 7.8): fetchmail before 6.3.6-rc4 does not properly enforce TLS and may transmit cleartext passwords over unsecured links if…
CVE-2005-4348 — High (CVSS 7.8): fetchmail before 6.3.1 and before 6.2.5.5, when configured for multidrop mode, allows remote attackers to cause a…
CVE-2002-1365 — High (CVSS 7.5): Heap-based buffer overflow in Fetchmail 6.1.3 and earlier does not account for the "@" character when determining…

All CVEs affecting Fetchmail →

Other CWE-909 vulnerabilities

CVE-2022-22704 — Critical (CVSS 9.8): The zabbix-agent2 package before 5.4.9-r1 for Alpine Linux sometimes allows privilege escalation to root because the…
CVE-2024-8178 — High (CVSS 8.8): The ctl_write_buffer and ctl_read_buffer functions allocated memory to be returned to userspace, without initializing…
CVE-2021-29980 — High (CVSS 8.8): Uninitialized memory in a canvas object could have caused an incorrect free() leading to memory corruption and a…
CVE-2021-23994 — High (CVSS 8.8): A WebGL framebuffer was not initialized early enough, resulting in memory corruption and an out of bound write. This…
CVE-2020-11741 — High (CVSS 8.8): An issue was discovered in xenoprof in Xen through 4.13.x, allowing guest OS users (with active profiling) to obtain…
CVE-2024-9780 — High (CVSS 7.8): ITS dissector crash in Wireshark 4.4.0 allows denial of service via packet injection or crafted capture file

Browse all CWE-909 vulnerabilities →