Is CVE-2021-44686 in the CISA KEV catalog?

No. CVE-2021-44686 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-44686?

CVE-2021-44686 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-44686?

CVE-2021-44686 has an EPSS score of 4.99% (91th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-44686?

Upgrade calibre on debian 11 to 5.12.0+dfsg-1+deb11u3 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2021-44686

HIGHEPSS 91th pctl

7.5

CVSS v3

NVD

Description

calibre before 5.32.0 contains a regular expression that is vulnerable to ReDoS (Regular Expression Denial of Service) in html_preprocess_rules in ebooks/conversion/preprocess.py.

CWE-400Resource Exhaustion

How to fix

Remediation Available

calibreDebian

Fixed in:5.12.0+dfsg-1+deb11u3CVE-2021-44686

Fixed in:5.33.0+dfsg-1CVE-2021-44686

calibreWindows application

Affected:5.32.0Fixed in:5.32.0Kovid Goyal

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

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

4.99%probability of exploitation in 30 days

91stpercentile

High risk: more likely to be exploited than 91% of all known CVEs.

References

Patch2

Exploit1

bugs.launchpad.net

Other references2

Related Vulnerabilities

Other CWE-400 (Resource Exhaustion) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-44487	High	7.5	100%	KEV	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2011-3192	High	7.8	99%	-	Fix
CVE-2019-11478	Medium	5.3	95%	-	Fix
CVE-2024-25617	Medium	5.3	89%	-	Fix
CVE-2018-1000115	High	7.5	89%	-	Fix

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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 2025-11-04.