libcurl 7.49.0 to and including 7.57.0 contains an out bounds read in code handling HTTP/2 trailers. It was reported (curl/curl#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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-1000005
• curl/curl#2231
• https://access.redhat.com/errata/RHSA-2019:1543
• https://curl.haxx.se/docs/adv_2018-824a.html
• https://usn.ubuntu.com/3554-1/
• https://www.debian.org/security/2018/dsa-4098
• http://www.securitytracker.com/id/1040273