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CVE-2019-11921

31
FAUCET Score

CVE-2019-11921 describes a critical out-of-bounds write vulnerability in Facebook's Proxygen library, affecting versions prior to v2019.07.22.00. This flaw arises from improper Base64 handling when parsing malformed binary content within Structured HTTP Headers, allowing an attacker to craft a special packet to trigger the vulnerability. With a CVSS score of 9.8 (CRITICAL), it presents a severe risk, enabling unauthenticated remote attackers to achieve high confidentiality, integrity, and availability impacts with low attack complexity. Despite its critical severity and significant community discussion (10 mentions), there is currently no evidence of active exploitation, nor are there publicly available Metasploit modules, Nuclei templates, or ExploitDB entries.

Impacted Technologies

VendorProductVersion(s)CPE
< v2019.07.22.00CPE match
cpe:2.3:a:facebook:proxygen:*:*:*:*:*:*:*:*
< 2019.07.22.00CPE matchmatch criteria
cpe:2.3:a:facebook:proxygen:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
2.08%
Probability of exploitation in next 30 days
EPSS Percentile
79.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0208 is in the 68th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / facebook/proxygen/commit/2f07985bef9fbae124cc63e5c0272e32da4fdaec
PatchThird Party Advisory
facebook.com / security/advisories/cve-2019-11921
Third Party Advisory