CVE-2021-24029: A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which c

Q: How do I fix CVE-2021-24029?

mvfst: upgrade to 2021-03-13; proxygen: upgrade to 2021.03.15.00. Exact commands for each OS are on this page.

Q: Is CVE-2021-24029 being exploited?

CVE-2021-24029 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-2021-24029 affect?

CVE-2021-24029 affects mvfst, proxygen. Severity is high (CVSS 7.5). A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a crash via a failed assertion. Per QUIC specification, this particular message should be treated as a connection error. Thi

Q: How urgent is CVE-2021-24029?

Priority 48/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADEUPGRADE

CVE-2021-24029 is a high-severity flaw (CVSS 7.5) affecting mvfst, proxygen. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a crash via a failed assertion. Per QUIC specification, this particular message should be treated as a connection error. This issue affects mvfst versions prior to commit a67083ff4b8dcbb7ee2839da6338032030d712b0 and proxygen versions prior to v2021.03.15.00.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.2% (top 32%)
CISA exploited list	No
Weakness	CWE-617
Published	2021-03-15
Last modified	2026-06-17

Publisher (CNA): Facebook, Inc. · Vendor: facebook

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

Am I affected?

Timeline

2021-03-15 22:15 UTCPublished CVE record published
2026-06-17 03:39 UTCUpdated Record last modified

facebook mvfst UPGRADE

Affected: < 2021-03-13

Fixed in: 2021-03-13

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2021-03-13 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mvfst

Note

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

facebook proxygen UPGRADE

Affected: < 2021.03.15.00

Fixed in: 2021.03.15.00

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2021.03.15.00 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade proxygen

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-2021-24029?

mvfst: upgrade to 2021-03-13; proxygen: upgrade to 2021.03.15.00. Exact commands for each OS are on this page.

Is CVE-2021-24029 being exploited?

CVE-2021-24029 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-2021-24029 affect?

CVE-2021-24029 affects mvfst, proxygen. Severity is high (CVSS 7.5). A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a crash via a failed assertion. Per QUIC specification, this particular message should be treated as a connection error. Thi

How urgent is CVE-2021-24029?

Priority 48/100. High severity; Remotely exploitable, no login, no user action

References

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