Is CVE-2021-3657 in the CISA KEV catalog?

No. CVE-2021-3657 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-3657?

CVE-2021-3657 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-3657?

CVE-2021-3657 has an EPSS score of 3.33% (87th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-3657?

Upgrade isync on debian 11 to 1.3.0-2.2+deb11u1 or later.

CVE & CISA-KEV Catalog

CVE-2021-3657

CRITICALEPSS 87th pctl

9.8

CVSS v3

NVD

Description

A flaw was found in mbsync versions prior to 1.4.4. Due to inadequate handling of extremely large (>=2GiB) IMAP literals, malicious or compromised IMAP servers, and hypothetically even external email senders, could cause several different buffer overflows, which could conceivably be exploited for remote code execution.

CWE-119Buffer Overflow

How to fix

Remediation Available

isyncDebian

Fixed in:1.3.0-2.2+deb11u1CVE-2021-3657

Fixed in:1.4.4-1CVE-2021-3657

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

3.33%probability of exploitation in 30 days

87thpercentile

Elevated risk: more likely to be exploited than 87% of all known CVEs.

References

Third-Party Advisory4

Related Vulnerabilities

Other CWE-119 (Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-4966	Critical	9.4	100%	KEV + Ransom	Fix
CVE-2017-11882	High	7.8	100%	KEV + Ransom	-
CVE-2020-0796	Critical	10.0	100%	KEV + Ransom	-
CVE-2008-4250	Critical	9.8	99%	KEV	-
CVE-2017-15944	Critical	9.8	98%	KEV	Fix
CVE-2015-0014	High	10.0	97%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.