CVE-2026-55099

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Source
https://cve.org/CVERecord?id=CVE-2026-55099
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55099.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-55099
Aliases
Published
2026-08-25T19:27:02Z
Modified
2026-11-15T02:46:48Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
icalendar: Algorithmic Complexity in Equality
Details

icalendar is an RFC 5545 compatible parser and generator of iCalendar files for Python. From 7.1.0 until 7.1.3, the Component equality method in src/icalendar/cal/component.py compares nested subcomponents with two membership loops, and each membership test invokes the same method on child components, causing O(2^n) work relative to nesting depth. Component.from_ical accepts arbitrarily nested BEGIN:VEVENT blocks without a depth limit, so an attacker can submit a sub-kilobyte .ics file containing equal nested subtrees and trigger the cost when an application performs equality, inequality, membership, deduplication, test-assertion, round-trip, or normalization comparisons. Parsing alone does not trigger the issue, and comparisons that differ early short-circuit, but a few hundred bytes can pin a CPU core for minutes or indefinitely, causing denial of service in calendar sync or import endpoints, invite processing, and other comparison paths. This issue is fixed in version 7.1.3.

Database specific 
{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-400",
        "CWE-407"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55099.json"
}
References

Affected packages

Git / github.com/collective/icalendar

Affected ranges

Type
GIT
Repo
https://github.com/collective/icalendar
Events
Introduced
1300b76fb3fe40d987cc3715735c026b3c1a2191
Fixed
f7240bc661548f9806c930f2a95ee2f003cfa8ca
Fixed
cad40cd112c93fd142ec12cc5b37445a849b8a79
Database specific
Show details 
{
    "extracted_events": [
        {
            "range": [
                {
                    "introduced": "7.1.0"
                },
                {
                    "fixed": "7.1.3"
                }
            ],
            "source": "AFFECTED_FIELD",
            "strategy": "StringRangeExpression"
        },
        {
            "range": [
                {
                    "fixed": "cad40cd112c93fd142ec12cc5b37445a849b8a79"
                }
            ],
            "source": "REFERENCES_COMMIT"
        },
        {
            "original_tag": "v7.1.3",
            "range": [
                {
                    "fixed": "f7240bc661548f9806c930f2a95ee2f003cfa8ca"
                }
            ],
            "source": "REFERENCES_TAG"
        }
    ]
}
Type
GIT
Repo
https://github.com/pycalendar/icalendar
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
b6b2608ae3af6de40695b4e40f71847485aa0b49
Database specific
Show details 
{
    "extracted_events": [
        {
            "range": [
                {
                    "fixed": "b6b2608ae3af6de40695b4e40f71847485aa0b49"
                }
            ],
            "source": "REFERENCES_COMMIT"
        }
    ]
}

Affected versions

2.*
2.2
3.*
3.0.1b1
3.0.1b2
3.1
3.10
3.11
3.11.1
3.11.2
3.11.3
3.11.4
3.11.5
3.11.6
3.11.7
3.12
3.1htug1
3.1htug2
3.2
3.3
3.4
3.4htug1
3.4htug2
3.4htug3
3.5
3.6
3.6.1
3.6.2
3.7
3.8
3.8.1
3.8.2
3.8.3
3.8.4
3.9.0
3.9.1
3.9.2
4.*
4.0.0
4.0.1
4.0.2
4.0.3
4.0.4
4.0.5
4.0.6
4.0.7
4.0.8
4.0.9
5.*
5.0.0a1
Other
before-timezone-refactoring
v5.*
v5.0.0
v5.0.1
v5.0.10
v5.0.11
v5.0.13
v5.0.2
v5.0.3
v5.0.4
v5.0.5
v5.0.6
v5.0.7
v5.0.8
v5.0.9
v6.*
v6.0.0
v6.0.0a0
v6.0.1
v6.1.0
v6.1.1
v6.1.2
v6.1.3
v6.2.0
v6.3.0
v6.3.1
v7.*
v7.0.0
v7.0.0a1
v7.0.0a2
v7.0.0a3
v7.0.1
v7.0.2
v7.0.3
v7.1.0
v7.1.1
v7.1.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55099.json"