CVE-2018-20615
Description
A flaw was found in HAProxy, versions before 1.8.17 and 1.9.1. Mishandling occurs when a priority flag is set on too short HEADERS frame in the HTTP/2 decoder, allowing an out-of-bounds read and a subsequent crash to occur. A remote attacker can exploit this flaw to cause a denial of service. Those who do not use HTTP/2 are unaffected.
Statement
HTTP/2 support was added to haproxy in version 1.8, therefore OpenShift Container Platform (OCP) 3.7 and earlier are unaffected by this flaw, see [1]. OCP 3.11 added a configuration option to ose-haproxy-router that made enabling HTTP/2 support easy, [2]. Prior to that, in versions OCP 3.9 and 3.10, an administrator had to customize the haproxy router configuration to add HTTP/2 support, [3]. OCP 3.9, and 3.10 are rated as moderate because HTTP/2 support was not a standard configuration option, and therefore unlikely to be enabled.
Versions of haproxy included in Red Hat Enterprise Linux 6 and 7, excluding rh-haproxy18-haproxy in Red Hat Software Collections, are unaffected as they package versions of haproxy before 1.7.
[1] http://www.haproxy.org/news.html
Mitigation
HTTP/2 support is disabled by default on OpenShift Container Platform 3.11. To mitigate this vulnerability keep it disabled. You can verify if HTTP/2 support is enabled by following the instructions in the upstream pull request, [1].
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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