#VU35171 Resource exhaustion in envoy - CVE-2019-15226

Vulnerability identifier: #VU35171

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2019-15226

CWE-ID: CWE-400

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
envoy
Server applications / IDS/IPS systems, Firewalls and proxy servers

Vendor: Cloud Native Computing Foundation

Description

The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.

Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

envoy: 1.0.0, 1.1.0 - 1.11.2, 1.2.0, 1.3.0, 1.4.0, 1.5.0, 1.6.0, 1.7.0 - 1.7.1, 1.8.0, 1.9.0 - 1.9.1

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External links
https://github.com/envoyproxy/envoy/commit/afc39bea36fd436e54262f150c009e8d72db5014
https://github.com/envoyproxy/envoy/commits/master
https://github.com/envoyproxy/envoy/issues/8520

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.