Threat Level: green Handler on Duty: Rob VandenBrink

SANS ISC: InfoSec Handlers Diary Blog - Internet Storm Center Diary 2019-04-25 InfoSec Handlers Diary Blog


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Unpatched Vulnerability Alert - WebLogic Zero Day

Published: 2019-04-25
Last Updated: 2019-04-25 15:23:54 UTC
by Rob VandenBrink (Version: 1)
3 comment(s)

The news today is full of a new deserialization vulnerability in Oracle WebLogic.  This affects all current versions of the product (the POC is against 10.3, but 12.x versions are also affected).  The vulnerability affects the wls9_async_response package (which is not included by default in all builds), so the workaround is to either ACL the Z/_async/* and /wls-wsat/* paths, or delete wls9_async_response.war.  A successful attack gets the attacker remote code exec on the vulnerable server.

The root cause here seems to be that the affected WAR components ingest and process all serialized data, and have a blacklist of "bad" content.  What this means to me is that we're likely to see a number of similar vulnerabilities / attacks crop up over the next while, until Oracle changes this approach.

Indications are that this is in the "tens of thousands" of affected sites, not hundreds or thousands or millions (not yet at least).

The vulnerability is posted as CNVD-2018-07811 (China National Vulnerability Database) at http://www.cnvd.org.cn/flaw/show/CNVD-2018-07811.  We don't have a CVE yet.

This bug was originally disclosed by the China Minsheng Banking Co.  There's a good write-up by the KnownSec 404 Team with  a bit more detail here: https://medium.com/@knownseczoomeye/knownsec-404-team-oracle-weblogic-deserialization-rce-vulnerability-0day-alert-90dd9a79ae93

This comes just one week after Oracle's "Patch Everything" Critical Patch Update (CPU) last week.  The next CPU isn't due for 3 months, so it'll be interesting to see what the out-of-band response patch or patches (if any) to this might be.

Stay tuned - we'll udpate this story as we get more information - in particular if we see attacks in the wild we'll post IoC's as we get them.

======= Update =======

Thanks to our reader who commented below!

The matching CVE number for this is CVE-2018-2628, which was identified as patched in last week's patches (Oracle's CPU - Critical Patch Updates).  However the POC mentioned was against a patched server, so I guess the patch isn't complete - nor can it be given Oracle's approach against this issue.

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