CVE-2021-44847: A stack-based buffer overflow in handle_request function in DHT.c in toxcore 0.1.9 through 0.1.11 and 0.2.0 th

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CRITICAL 9.8REMOTEUPGRADEMITIGATE

CVE-2021-44847 is a critical-severity flaw (CVSS 9.8) affecting toxcore, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A stack-based buffer overflow in handle_request function in DHT.c in toxcore 0.1.9 through 0.1.11 and 0.2.0 through 0.2.12 (caused by an improper length calculation during the handling of received network packets) allows remote attackers to crash the process or potentially execute arbitrary code via a network packet.

Why this priority

Critical severity
EPSS top 9%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	4.1% (top 9%)
CISA exploited list	No
Weakness	CWE-682
Published	2021-12-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · toktok

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

Am I affected?

Timeline

2021-12-13 01:15 UTCPublished CVE record published
2026-06-17 04:12 UTCUpdated Record last modified

toktok toxcore UPGRADE

Affected: >= 0.1.9 and <= 0.1.11 · >= 0.2.0 and <= 0.2.12

Fixed in: newer than 0.2.12

Safe to downgrade to: a release before 0.1.9

1. Check installed version

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

2. UPGRADE to newer than 0.2.12 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade toxcore

Note

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

3. If no update is available yet, DOWNGRADE to a release before 0.1.9 (Debian / Ubuntu)

apt-cache madison toxcore sudo apt install toxcore=<VERSION_BEFORE_0.1.9> sudo apt-mark hold toxcore

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list toxcore sudo dnf downgrade toxcore-<VERSION_BEFORE_0.1.9> sudo dnf versionlock add toxcore

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: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

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-2021-44847?

toxcore: upgrade to newer than 0.2.12; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-44847 being exploited?

CVE-2021-44847 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-2021-44847 affect?

CVE-2021-44847 affects toxcore, fedora. Severity is critical (CVSS 9.8). A stack-based buffer overflow in handle_request function in DHT.c in toxcore 0.1.9 through 0.1.11 and 0.2.0 through 0.2.12 (caused by an improper length calculation during the handling of received network packets) allows remote attackers to

How urgent is CVE-2021-44847?

Priority 67/100. Critical severity; EPSS top 9%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

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References

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