Is CVE-2021-26929 in the CISA KEV catalog?

No. CVE-2021-26929 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-26929?

CVE-2021-26929 has a CVSS v3 base score of 6.1 (MEDIUM).

What is the EPSS score for CVE-2021-26929?

CVE-2021-26929 has an EPSS score of 4.94% (91th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-26929?

Upgrade php-horde-text-filter on debian 11 to 2.3.7-1 or later.

CVE & CISA-KEV Catalog

CVE-2021-26929

MEDIUMEPSS 91th pctl

6.1

CVSS v3

NVD

Description

An XSS issue was discovered in Horde Groupware Webmail Edition through 5.2.22 (where the Horde_Text_Filter library before 2.3.7 is used). The attacker can send a plain text e-mail message, with JavaScript encoded as a link or email that is mishandled by preProcess in Text2html.php, because bespoke use of \x00\x00\x00 and \x01\x01\x01 interferes with XSS defenses.

CWE-79Cross-Site Scripting (XSS)

How to fix

Remediation Available

php-horde-text-filterDebian

Fixed in:2.3.7-1CVE-2021-26929

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 InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

4.94%probability of exploitation in 30 days

91stpercentile

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

References

Exploit2

Vendor Advisory2

Third-Party Advisory3

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	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 2024-11-21.