CVE-2018-1000005: Canonical Ubuntu Linux

Critical severity, CVSS 9.1. EPSS: 4.6% chance of exploitation in the next 30 days.

libcurl 7.49.0 to and including 7.57.0 contains an out bounds read in code handling HTTP/2 trailers. It was reported (https://github.com/curl/curl/pull/2231) that reading an HTTP/2 trailer could mess up future trailers since the stored size was one byte less than required. The problem is that the code that creates HTTP/1-like headers from the HTTP/2 trailer data once appended a string like `:` to the target buffer, while this was recently changed to `: ` (a space was added after the colon) but the following math wasn't updated correspondingly. When accessed, the data is read out of bounds and causes either a crash or that the (too large) data gets passed to client write. This could lead to a denial-of-service situation or an information disclosure if someone has a service that echoes back or uses the trailers for something.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 17.10 only
• Debian Debian Linux: version 8.0 only; version 9.0 only
• Haxx Libcurl: from 7.49.0, up to and including 7.57.0

Published 2018-01-24. Last modified 2026-06-17.