What is CVE-2026-33635?

CVE-2026-33635 is a medium-severity vulnerability in Icalendar, classified under CRLF Injection. CVSS score: 4.3/10. Published 2026-03-26.

How severe is CVE-2026-33635?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in Icalendar

CVE-2026-33635

iCalendar is a Ruby library for dealing with iCalendar files in the iCalendar format defined by RFC-5545. Starting in version 2.0.0 and prior to version 2.12.2, .ics serialization does not properly sanitize URI property values, enabling IC…

Vulnerability class: CRLF Injection

EPSS: 0.001 (16.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.

Affected products

Icalendar — versions >= 2.0.0, < 2.12.2

Weakness classification (CWE)

CWE-93 — CRLF Injection

References

https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq (x_refsource_CONFIRM)
https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265 (x_refsource_MISC)
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-33635?: CVE-2026-33635 is a medium-severity vulnerability in Icalendar, classified under CRLF Injection. CVSS score: 4.3/10. Published 2026-03-26.
How severe is CVE-2026-33635?: Medium severity. CVSS v3 base score is 4.3 out of 10.