Proxygen
CVE-2019-11921
CRITICAL
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, write limits
MITRE ATT&CK
2 techniques across 2 tactics: Execution, Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. |
| Exploit ScenarioDerived | A remote attacker could write data beyond allocated buffer boundaries leading to code execution or crashes by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
Get an e-mail when this CVE is exploited, patched or re-scored. Free account.
Alert meAnalysisAI
An out of bounds write is possible via a specially crafted packet in certain configurations of Proxygen due to improper handling of Base64 when parsing malformed binary content in Structured HTTP. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Write vulnerability could allow attackers to write data beyond allocated buffer boundaries leading to code execution or crashes.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Validate write boundaries, use memory-safe languages, enable compiler protections (ASLR, stack canaries).
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Out-of-bounds Write (CWE-787), which allows attackers to write data beyond allocated buffer boundaries leading to code execution or crashes. An out of bounds write is possible via a specially crafted packet in certain configurations of Proxygen due to improper handling of Base64 when parsing malformed binary content in Structured HTTP Headers.07.22.00. Affected products include: Facebook Proxygen.
Know when Proxygen gets its next vulnerability
- Watch products and get an email when something new is published
- Check this CVE against your own stack and servers
- Exploit and PoC references, threat intelligence from 22 sources
No credit card · 7-day full trial
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
An out of bounds write is possible via a specially crafted packet in certain configurations of Proxygen due to improper handling of Base64 when parsing malformed binary content in Structured HTTP Headers. This issue affects versions of proxygen prior to v2019.07.22.00.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.
Affected Products (CPE)NVD
Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour
The SPDY/2 codec in Facebook Proxygen before 2015-11-09 truncates a certain field to two bytes, which allows hijacking a
A use-after-free is possible due to an error in lifetime management in the request adaptor when a malicious client invok
In the course of decompressing HPACK inside the HTTP2 protocol, an unexpected sequence of header table resize operations
Facebook Proxygen before 2015-11-09 mismanages HTTPMessage.request state, which allows remote attackers to conduct hijac
The SPDY/2 codec in Facebook Proxygen before 2015-11-09 allows remote attackers to conduct hijacking attacks and bypass
Use-after-free in Meta's Proxygen HTTP library (v2024.10.28.00 through v2026.09.28.00) lets remote, unauthenticated atta
A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a cr
An issue in the Proxygen handling of HTTP2 parsing of headers/trailers can lead to a denial-of-service attack. Rated hig
A potential denial-of-service issue in the Proxygen handling of invalid HTTP2 priority settings (specifically a circular
Proxygen fails to validate that a secondary auth manager is set before dereferencing it. Rated high severity (CVSS 7.5),
Use-after-free in Meta's proxygen C++ networking library (versions v2026.04.06.00 up to but not including v2026.09.28.00
Exploit-DB