Date: Fri, 15 Oct 2021 20:00:59 +0200 From: Roman Medina-Heigl Hernandez <roman@...labs.com> To: Yann Ylavic <ylavic.dev@...il.com> Cc: oss-security@...ts.openwall.com Subject: Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) Hi Yann, Re , I think this: "critical: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 (CVE-2021-41773 <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-41773>)" is still misleading and should read: "critical: Path traversal and *Remote Code Execution* vulnerability in Apache HTTP Server 2.4.49 (CVE-2021-41773 <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-41773>)" PS: Dear Alexander, feel free to drop this from OSS-ml if you think this kind of detail is not relevant. Cheers, -r El 11/10/2021 a las 10:57, Yann Ylavic escribió: > On Sat, Oct 9, 2021 at 8:00 PM Roman Medina-Heigl Hernandez > <roman@...labs.com> wrote: >> I just wanted to clarify that the impact of both CVEs is exactly the >> same: RCE and/or arbitrary file read and/or none, depending on httpd >> config :-). > I appreciate this nuance in your tweetS. For completeness :) I'll note > that most configs (default, vendors, distros) are not vulnerable to > the RCE. > The removal of "<Directory/> require all denied" is an exploit httpd > can do nothing about. httpd provides default/examples config  and > docs (no "don't do that" there I concede). > >> There's no difference between Apache 2.4.49 and 2.4.50 in >> that regard. > Ack. > >> But reading the blog post by Stefan >> (https://github.com/icing/blog/blob/main/httpd-2.4.50.md) and Apache >> HTTP 2.4 vulns security page >> (https://httpd.apache.org/security/vulnerabilities_24.html) as well, I >> feel like you are associating the RCE impact to 2.4.50 and the arbitrary >> file read to 2.4.49. That's misleading. Examples: > I feel obligated to Alexander and reference , plain text of the > current httpd vulnerabilities (w.r.t. CVE-2021-42013 & > CVE-2021-41773), as of "Fri, 8 Oct 2021 15:44:24 +0200" . > >> - blog post >> >> "Affection, 2.4.49" -> You go for arbitrary file read example. >> >> "Affection, 2.4.50" -> Then you go for RCE example. > The blog port has the form of a chronological post mortem (it happened > in this order from the httpd team POV), it's an editorial choice (by > Stefan) which makes sense to me as it describes the case progressively > and finally quite exhaustively. > It's not the same goal as the vulnerabilities page anyway. > >> - security page > Please see , both CVEs are aligned now. > >> I'm sure this is unintentional and yes, it's only matter of wording but >> it's kind of misleading, imho. I'd kindly advise for it to be fixed. > That's the case (I think) on the vulnerabilities page now. > >> And >> I also take this opportunity to thank ASF and particularly the folks >> like Yann and Stefan whose work makes Apache httpd possible. >> >> C'u in apache-nosejob-202x.c !!! :-) > Thanks for the kind words! Well, I suppose :) > > Regards; > Yann. > > >  https://httpd.apache.org/security/vulnerabilities_24.html (8 Oct) : > """ > critical: Path Traversal and Remote Code Execution in Apache HTTP > Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) > (CVE-2021-42013) > > It was found that the fix for CVE-2021-41773 in Apache HTTP Server > 2.4.50 was insufficient. An attacker could use a path traversal attack > to map URLs to files outside the directories configured by Alias-like > directives. > > If files outside of these directories are not protected by the > usual default configuration "require all denied", these requests can > succeed. If CGI scripts are also enabled for these aliased paths, this > could allow for remote code execution. > > This issue only affects Apache 2.4.49 and Apache 2.4.50 and not > earlier versions. > > Acknowledgements: > > Reported by Juan Escobar from Dreamlab Technologies > Reported by Fernando Muñoz from NULL Life CTF Team > Reported by Shungo Kumasaka > Reported by Nattapon Jongcharoen > > Reported to security team 2021-10-06 > fixed by r1893977, r1893980, r1893982 in 2.4.x 2021-10-07 > Update 2.4.51 released 2021-10-07 > Affects 2.4.50, 2.4.49 > > critical: Path traversal and file disclosure vulnerability in Apache > HTTP Server 2.4.49 (CVE-2021-41773) > > A flaw was found in a change made to path normalization in Apache > HTTP Server 2.4.49. An attacker could use a path traversal attack to > map URLs to files outside the directories configured by Alias-like > directives. > > If files outside of these directories are not protected by the > usual default configuration "require all denied", these requests can > succeed. If CGI scripts are also enabled for these aliased paths, this > could allow for remote code execution. > > This issue is known to be exploited in the wild. > > This issue only affects Apache 2.4.49 and not earlier versions. > > Acknowledgements: This issue was reported by Ash Daulton along > with the cPanel Security Team > Reported to security team 2021-09-29 > fixed by r1893775 in 2.4.x 2021-10-01 > Update 2.4.50 released 2021-10-04 > Affects 2.4.49 > """ > >  https://github.com/apache/httpd-site/commit/74a166fab7443838c660c88df81961ddaa8df7fd.patch > : > """ > Date: Fri, 8 Oct 2021 15:44:24 +0200 > Subject: [PATCH] Revert "Trigger rebuild" > > This reverts commit 151e1ff7cdacf68fc615cc1513dbf81b8f307907. > --- > content/security/json/CVE-2021-42013.json | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/content/security/json/CVE-2021-42013.json > b/content/security/json/CVE-2021-42013.json > index 09b4792..31e9295 100644 > --- a/content/security/json/CVE-2021-42013.json > +++ b/content/security/json/CVE-2021-42013.json > @@ -112,4 +112,3 @@ > } > ] > } > - > """ > To make sure every single byte was published :) > >  https://github.com/apache/httpd/blob/2.4.x/docs/conf/httpd.conf.in#L110 : > """ > # > # Deny access to the entirety of your server's filesystem. You must > # explicitly permit access to web content directories in other > # <Directory> blocks below. > # > <Directory /> > AllowOverride none > Require all denied > </Directory> > """ -- Saludos, -Román
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