PatchTheCVECVE-2016-5824: libical 1.0 allows remote attackers to cause a denial of service (use-after-free) via a crafted ics file.
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MEDIUM 5.5WATCHLISTDOWNGRADEMITIGATEMITIGATE
CVE-2016-5824 is a medium-severity flaw (CVSS 5.5) affecting libical, ubuntu linux, enterprise linux desktop. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
libical 1.0 allows remote attackers to cause a denial of service (use-after-free) via a crafted ics file.
Why this priority
- On your watchlist
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 5.5 (Medium) |
| Attack vector | Local |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 2.2% (top 18%) |
| CISA exploited list | No |
| Weakness | CWE-416 |
| Published | 2017-01-27 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
libical project libical DOWNGRADE
Affected: 1.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 1.0
1. Check installed version
apt-cache policy libical || rpm -q libical || libical --version
2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)
apt-cache madison libical
sudo apt install libical=<VERSION_BEFORE_1.0>
sudo apt-mark hold libical
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list libical
sudo dnf downgrade libical-<VERSION_BEFORE_1.0>
sudo dnf versionlock add libical
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
canonical ubuntu linux MITIGATE
Affected: 14.04 · 16.04 · 18.04 · 18.10
Fixed in: no fixed release known
Safe to downgrade to: a release before 14.04
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
redhat enterprise linux desktop MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
redhat enterprise linux server MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
redhat enterprise linux server aus MITIGATE
Affected: 7.6
Fixed in: no fixed release known
Safe to downgrade to: a release before 7.6
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
redhat enterprise linux server eus MITIGATE
Affected: 7.6
Fixed in: no fixed release known
Safe to downgrade to: a release before 7.6
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
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.
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-2016-5824?
libical: downgrade or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation; enterprise linux desktop: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2016-5824 being exploited?
CVE-2016-5824 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-2016-5824 affect?
CVE-2016-5824 affects libical, ubuntu linux, enterprise linux desktop. Severity is medium (CVSS 5.5). libical 1.0 allows remote attackers to cause a denial of service (use-after-free) via a crafted ics file.
How urgent is CVE-2016-5824?
Priority 45/100. On your watchlist
Software pages
Related CVEs
- CVE-2016-9584 CRITICAL 9.1 UPGRADE libical allows remote attackers to cause a denial of service (use-after-free) and possibly read heap memory vi
- 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-2016-5823 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