// For flags

CVE-2021-43848

Unititialized memory access in h2o

Severity Score

5.9
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

h2o is an open source http server. In code prior to the `8c0eca3` commit h2o may attempt to access uninitialized memory. When receiving QUIC frames in certain order, HTTP/3 server-side implementation of h2o can be misguided to treat uninitialized memory as HTTP/3 frames that have been received. When h2o is used as a reverse proxy, an attacker can abuse this vulnerability to send internal state of h2o to backend servers controlled by the attacker or third party. Also, if there is an HTTP endpoint that reflects the traffic sent from the client, an attacker can use that reflector to obtain internal state of h2o. This internal state includes traffic of other connections in unencrypted form and TLS session tickets. This vulnerability exists in h2o server with HTTP/3 support, between commit 93af138 and d1f0f65. None of the released versions of h2o are affected by this vulnerability. There are no known workarounds. Users of unreleased versions of h2o using HTTP/3 are advised to upgrade immediately.

h2o es un servidor http de código abierto. En el código anterior al commit "8c0eca3" h2o puede intentar acceder a memoria no inicializada. Cuando son recibidas tramas QUIC en determinado orden, la implementación del lado del servidor HTTP/3 de h2o puede equivocarse al tratar la memoria no inicializada como tramas HTTP/3 que se han recibido. Cuando h2o es usado como un proxy inverso, un atacante puede abusar de esta vulnerabilidad para enviar el estado interno de h2o a servidores backend controlados por el atacante o por terceros. Además, si se presenta un endpoint HTTP que refleja el tráfico enviado desde el cliente, un atacante puede usar ese reflector para obtener el estado interno de h2o. Este estado interno incluye el tráfico de otras conexiones en forma no encriptada y los tickets de sesión TLS. Esta vulnerabilidad se presenta en el servidor h2o con soporte HTTP/3, entre el commit 93af138 y el d1f0f65. Ninguna de las versiones liberadas de h2o está afectada por esta vulnerabilidad. No se conocen medidas de mitigación adicionales. Se recomienda a usuarios de versiones no liberadas de h2o que usen HTTP/3 que actualicen inmediatamente

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
Partial
Integrity
None
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-11-16 CVE Reserved
  • 2022-02-01 CVE Published
  • 2024-08-04 CVE Updated
  • 2024-10-17 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-908: Use of Uninitialized Resource
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Dena
Search vendor "Dena"
 H2o
Search vendor "Dena" for product "H2o"
 < 2021-12-20
Search vendor "Dena" for product "H2o" and version " < 2021-12-20"
-
Affected