No exploitation reportedFix available

CVE-2021-24029

Q: Is CVE-2021-24029 actively exploited?

Active exploitation of CVE-2021-24029 has not been confirmed. Its EPSS score was 1.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-24029?

CVE-2021-24029 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

No exploitation reported by the sources we read.

Published2021-03-15
Fixed in2021-03-13
WeaknessCWE-617

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2021-03-1522:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-24029?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-24029?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Facebook mvfst

Branch	Affected	Fixed in	Source
2021.x	< 2021-03-13	2021-03-13	NVD

Facebook proxygen

Branch	Affected	Fixed in	Source
2021.3	< 2021.03.15.00	2021.03.15.00	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Facebook mvfst to 2021-03-13

Advisories and patches

github.comPatch
www.facebook.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.17.5read 2026-10-23
NVDCVSS 2.05read 2026-10-23
CNAweakness (CWE)CWE-617read 2026-10-23
NVDweakness (CWE)CWE-617read 2026-10-23
FIRST EPSSEPSS score1.2 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2021-03-15
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-24029?

Is CVE-2021-24029 actively exploited?

Active exploitation of CVE-2021-24029 has not been confirmed. Its EPSS score was 1.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-24029?

CVE-2021-24029 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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