CVE-2016-5826 Libical Project CVE debrief

Who should care

Teams that ship or embed libical, especially applications and services that parse untrusted iCalendar data. This includes calendar servers, mail clients, scheduling systems, and any downstream product that depends on libical 0.47 or 1.0.

Technical summary

According to the NVD record, the vulnerable path is parser_get_next_char in libical when handling input to icalparser_parse_string. Crafted input can cause the parser to read beyond heap bounds, creating a remote denial-of-service condition. The published CVSS v3.0 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, which matches a network-reachable crash-style impact without confidentiality or integrity effects.

Defensive priority

High. The bug is remotely triggerable, requires no privileges or user interaction, and has high availability impact. Prioritize if libical is exposed to external or semi-trusted calendar content.

Recommended defensive actions

• Update or replace affected libical deployments with a vendor or upstream release that addresses CVE-2016-5826.
• Inventory products and services that bundle libical 0.47 or 1.0, including transitive dependencies.
• Treat calendar and scheduling input as untrusted and validate or sandbox parsing paths where possible.
• Monitor for parser crashes or repeated restart events that could indicate malformed-input handling issues.
• If immediate patching is not possible, reduce exposure by limiting which systems can submit iCalendar content to affected services.

Evidence notes

The supplied NVD record identifies the flaw as an out-of-bounds heap read (CWE-125) in libical, affecting versions 0.47 and 1.0. The reference set includes an Openwall oss-security post dated 2016-06-25, a SecurityFocus BID entry, and a Mozilla Bugzilla issue for tracking. The CVE was published on 2017-01-27; that publication date is the correct timeline anchor for this debrief.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.