CVE-2016-9584: libical allows remote attackers to cause a denial of service (use-after-free) and possibly read heap memory vi

Q: How do I fix CVE-2016-9584?

libical: upgrade to newer than 2.0. Exact commands for each OS are on this page.

Q: Is CVE-2016-9584 being exploited?

CVE-2016-9584 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2016-9584 affect?

CVE-2016-9584 affects libical. Severity is critical (CVSS 9.1). libical allows remote attackers to cause a denial of service (use-after-free) and possibly read heap memory via a crafted ics file.

Q: How urgent is CVE-2016-9584?

Priority 58/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2016-9584 is a critical-severity flaw (CVSS 9.1) affecting libical. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libical allows remote attackers to cause a denial of service (use-after-free) and possibly read heap memory via a crafted ics file.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.3% (top 17%)
CISA exploited list	No
Weakness	CWE-416
Published	2017-01-18
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: libical project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2017-01-18 17:59 UTCPublished CVE record published
2026-06-17 00:56 UTCUpdated Record last modified

libical project libical UPGRADE

Affected: <= 2.0

Fixed in: newer than 2.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libical || rpm -q libical || libical --version

2. UPGRADE to newer than 2.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libical

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libical

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2016-9584?

libical: upgrade to newer than 2.0. Exact commands for each OS are on this page.

Is CVE-2016-9584 being exploited?

CVE-2016-9584 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2016-9584 affect?

CVE-2016-9584 affects libical. Severity is critical (CVSS 9.1). libical allows remote attackers to cause a denial of service (use-after-free) and possibly read heap memory via a crafted ics file.

How urgent is CVE-2016-9584?

Priority 58/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2016-5827 HIGH 7.5 DOWNGRADE The icaltime_from_string function in libical 0.47 and 1.0 allows remote attackers to cause a denial of service
CVE-2016-5826 HIGH 7.5 DOWNGRADE The parser_get_next_char function in libical 0.47 and 1.0 allows remote attackers to cause a denial of service
CVE-2016-5825 MEDIUM 5.5 DOWNGRADE The icalparser_parse_string function in libical 0.47 and 1.0 allows remote attackers to cause a denial of serv
CVE-2016-5824 MEDIUM 5.5 DOWNGRADE MITIGATE libical 1.0 allows remote attackers to cause a denial of service (use-after-free) via a crafted ics file.
CVE-2016-5823 MEDIUM 5.5 DOWNGRADE The icalproperty_new_clone function in libical 0.47 and 1.0 allows remote attackers to cause a denial of servi

References

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