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PatchSiren cyber security CVE debrief

CVE-2016-5824 Redhat CVE debrief

CVE-2016-5824 affects libical 1.0 and can be triggered by a crafted .ics file, resulting in a denial of service through a use-after-free condition. NVD assigns a medium CVSS score (5.5) with high availability impact, and the official vector indicates user interaction is required. Organizations that parse calendar data or ship libical-based packages should treat this as a patching issue rather than a theoretical parser bug.

Vendor
Redhat
Product
CVE-2016-5824
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2017-01-27
Original CVE updated
2026-05-13
Advisory published
2017-01-27
Advisory updated
2026-05-13

Who should care

Administrators and developers running libical 1.0 or downstream packages that process .ics files, especially on affected Ubuntu and Red Hat Enterprise Linux platforms listed in NVD. Security teams responsible for desktop, mail, calendar, or file-import workflows that accept untrusted calendar content should also review exposure.

Technical summary

NVD records the weakness as CWE-416 (use-after-free). The vulnerability is described as a crafted .ics file causing denial of service in libical 1.0. The CVSS 3.0 vector is AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H, which means the primary documented impact is availability loss and exploitation depends on user interaction. NVD also lists libical_project:libical 1.0 and several downstream OS CPEs as vulnerable.

Defensive priority

Medium: the impact is availability-focused and the CVSS score is moderate, but the issue is still important anywhere untrusted .ics files may be opened or imported.

Recommended defensive actions

  • Inventory systems and applications that bundle or depend on libical 1.0.
  • Apply vendor fixes or security updates referenced by the NVD record for your platform (for example Red Hat and Ubuntu advisories where applicable).
  • Prioritize patching user-facing applications and services that open, import, or parse untrusted .ics files.
  • Restrict or sanitize handling of externally supplied calendar files until patched versions are deployed.
  • Validate downstream package status on supported distributions rather than assuming the base library alone determines exposure.

Evidence notes

The debrief is based on the official NVD record and the supplied CVE metadata. NVD describes the issue as a libical 1.0 use-after-free leading to denial of service, maps it to CWE-416, and lists libical 1.0 plus multiple downstream OS CPEs as vulnerable. The references include OSS-security mailing list entries, libical issue tracker items, and vendor advisories from Red Hat, Ubuntu, and Gentoo. The CVSS vector supplied by NVD indicates user interaction is required.

Official resources

Publicly disclosed in the CVE/NVD record on 2017-01-27. The supplied NVD record was later modified on 2026-05-13; that modified date reflects record maintenance, not the original vulnerability date.