curl / Docs / Security / HTTP/2 trailer out-of-bounds read

HTTP/2 trailer out-of-bounds read

Project curl Security Advisory, January 24th 2018 - Permalink

VULNERABILITY

libcurl contains an out bounds read in code handling HTTP/2 trailers.

It was reported 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 associated 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 the libcurl callback. This might 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.

We are not aware of any exploit of this flaw.

INFO

This bug was introduced in commit 0761a51ee0551ad9e5, May 11 2016.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2018-1000005 to this issue.

AFFECTED VERSIONS

libcurl is used by many applications, but not always advertised as such.

THE SOLUTION

In libcurl version 7.58.0, the allocation size is corrected.

A patch for CVE-2018-1000005 is available.

RECOMMENDATIONS

We suggest you take one of the following actions immediately, in order of preference:

A - Upgrade curl to version 7.58.0

B - Apply the patch to your version and rebuild

TIME LINE

It was publicly reported to the curl project on January 10, 2018.

The security impact was realized and assessed on January 11. The fix was merged publicly in git on the same day, not mentioning the security impact.

We contacted distros@openwall on January 17.

curl 7.58.0 was released on January 24 2018, coordinated with the publication of this advisory.

CREDITS

Reported and patched by Zhouyihai Ding. Researched by Ray Satiro.

Thanks a lot!