Bug 1605052 (CVE-2018-8011)

Summary: CVE-2018-8011 httpd: mod_md: NULL pointer dereference causing httpd child process crash
Product: [Other] Security Response Reporter: Sam Fowler <sfowler>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abhgupta, anon.amish, bmaxwell, bmcclain, cdewolf, chazlett, cmacedo, csutherl, darran.lofthouse, dbaker, dblechte, dfediuck, dffrench, dimitris, dosoudil, drusso, eedri, fgavrilo, gzaronik, hhorak, jawilson, jclere, jdoyle, jkaluza, jmadigan, jokerman, jondruse, jorton, jshepherd, lgao, lgriffin, luhliari, mbabacek, mgoldboi, michal.skrivanek, mturk, myarboro, ngough, pahan, pgier, pjurak, ppalaga, psakar, pslavice, pwright, rnetuka, rstancel, rsvoboda, sbonazzo, sherold, sstavrev, sthangav, trankin, trepel, twalsh, vtunka, weli
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: httpd 2.4.34 Doc Type: If docs needed, set a value
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Story Points: ---
Clone Of: Environment:
Last Closed: 2019-06-10 10:33:44 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1605093, 1605094    
Bug Blocks: 1605053    
Attachments:
Description Flags
mod_md CVE-2018-8011 patch none

Description Sam Fowler 2018-07-20 04:56:25 UTC 
Apache httpd before version 2.4.34 has a vulnerability in mod_md. By specially crafting HTTP requests, the mod_md challenge handler would dereference a NULL pointer and cause the child process to segfault. This could be used to DoS the server.


External References:

https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2018-8011
Comment 1 Tomas Hoger 2018-07-20 07:32:23 UTC 
The affected mod_md module was only introduced upstream in version 2.4.30 as an experimental module:

  *) mod_md: new experimental, module for managing domains across virtual hosts,
     implementing the Let's Encrypt ACMEv1 protocol to signup and renew 
     certificates. Please read the modules documentation for further instructions
     on how to use it. [Stefan Eissing]

http://archive.apache.org/dist/httpd/CHANGES_2.4.32
https://httpd.apache.org/docs/2.4/mod/mod_md.html

Note that versions 2.4.30 and 2.4.31 were not released, so the first released version with this functionality was 2.4.32.
Comment 2 Tomas Hoger 2018-07-20 07:34:01 UTC 
Created httpd tracking bugs for this issue:

Affects: fedora-all [bug 1605093]
Comment 5 Tomas Hoger 2018-07-20 09:07:04 UTC 
This should be the patch, as applied to the mod_md git repo:

https://github.com/icing/mod_md/commit/e71001955809247b3aa4d269e1e0741b4fe0fc3d

It notes the following fix for the mod_md 1.1.11:

  * fixes a Null Dereference when specially crafted requests are sent to the
    server. Reported by Daniel Caminada <daniel.caminada>.

However, that commit includes additional unrelated changes (from mod_md 1.1.12).  The relevant part should be the second and the third change to the mod_md.c file.

The fix integrated to httpd trunk via this commit:

http://svn.apache.org/viewvc?view=revision&revision=1832935
https://github.com/apache/httpd/commit/7bd724657c3b0a4a6016ca72f1be26ac9ebd8cd2

The fix to the 2.4 branch was even combined with lot of other changes, updating mod_md from version 1.0.8 to 1.1.15:

https://github.com/apache/httpd/commit/acfdb68fb80618fe5af06dcfa1dd8ca7b0e6d76d
Comment 6 Joe Orton 2018-07-20 09:27:05 UTC 
Created attachment 1464893 [details]
mod_md CVE-2018-8011 patch

According to (previously private) discussion at security.org, the specific fix for the mod_md issue is as attached. I am making it public here for full disclosure.