CVE-2021-36979: Unicorn Engine 1.0.2 has an out-of-bounds write in tb_flush_armeb (called from cpu_arm_exec_armeb and tcg_cpu_

Routine

MEDIUM 5.5DOWNGRADEMITIGATE

CVE-2021-36979 is a medium-severity flaw (CVSS 5.5) affecting unicorn engine, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Unicorn Engine 1.0.2 has an out-of-bounds write in tb_flush_armeb (called from cpu_arm_exec_armeb and tcg_cpu_exec_armeb).

Why this priority

No elevated risk signals yet

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	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-07-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · unicorn-engine

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

Am I affected?

Timeline

2021-07-20 07:15 UTCPublished CVE record published
2026-06-17 03:59 UTCUpdated Record last modified

unicorn-engine unicorn engine DOWNGRADE

Affected: 1.0.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.2

1. Check installed version

apt-cache policy unicorn-engine || rpm -q unicorn-engine || unicorn-engine --version

2. No fixed release: DOWNGRADE to a release before 1.0.2 (Debian / Ubuntu)

apt-cache madison unicorn-engine sudo apt install unicorn-engine=<VERSION_BEFORE_1.0.2> sudo apt-mark hold unicorn-engine

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list unicorn-engine sudo dnf downgrade unicorn-engine-<VERSION_BEFORE_1.0.2> sudo dnf versionlock add unicorn-engine

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.

fedoraproject fedora MITIGATE

Affected: 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 35

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.

Quick answers

How do I fix CVE-2021-36979?

unicorn engine: downgrade or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-36979 being exploited?

CVE-2021-36979 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-2021-36979 affect?

CVE-2021-36979 affects unicorn engine, fedora. Severity is medium (CVSS 5.5). Unicorn Engine 1.0.2 has an out-of-bounds write in tb_flush_armeb (called from cpu_arm_exec_armeb and tcg_cpu_exec_armeb).

How urgent is CVE-2021-36979?

Priority 34/100. No elevated risk signals yet.

Related CVEs

CVE-2022-29695 HIGH 7.5 UPGRADE Unicorn Engine v2.0.0-rc7 contains memory leaks caused by an incomplete unicorn engine initialization.
CVE-2022-29694 HIGH 7.5 UPGRADE Unicorn Engine v2.0.0-rc7 and below was discovered to contain a NULL pointer dereference via qemu_ram_free.
CVE-2022-29693 HIGH 7.5 UPGRADE Unicorn Engine v2.0.0-rc7 and below was discovered to contain a memory leak via the function uc_close at /my/u
CVE-2022-29692 HIGH 7.8 DOWNGRADE Unicorn Engine v1.0.3 was discovered to contain a use-after-free vulnerability via the hook function.
CVE-2021-44078 HIGH 8.1 UPGRADE An issue was discovered in split_region in uc.c in Unicorn Engine before 2.0.0-rc5

References

← Back to latest CVEs