Email Security

Google Patches Email Spoofing Vulnerability After Public Disclosure

Google released a patch for an email spoofing vulnerability affecting Gmail and G Suite seven hours after it was publicly disclosed, but the tech giant knew about the flaw since April.

Eduard Kovacs

August 20, 2020

Google released a patch for an email spoofing vulnerability affecting Gmail and G Suite seven hours after it was publicly disclosed, but the tech giant knew about the flaw since April.

The vulnerability was disclosed on Wednesday by researcher Allison Husain, who described her findings in a blog post and shared proof-of-concept (PoC) code. The issue, related to missing verifications when configuring mail routes, could have been exploited by an attacker to send an email as another Gmail or G Suite user while bypassing protection mechanisms such as DMARC and SPF.

Husain demonstrated her findings by using her personal G Suite domain to send an email apparently coming from an @google.com address to a G Suite email account on a domain she did not control.

“I chose to send to another G Suite account to demonstrate that Google’s strong mail filtering and anti-spam techniques do not block or detect this attack,” the researcher explained. “Additionally, I chose to impersonate google.com because their DMARC policy is set to p=reject and so any violations of SPF (regardless of the SPF policy) should result in the message simply being dropped with prejudice.”

The attack leveraged a weakness related to mail routing rules, which an attacker could have abused to “relay and grant authenticity to fraudulent messages.”

The security hole was reported to Google on April 3 and the company confirmed it on April 16, when it assigned priority and severity ratings of “2.” Google later marked the flaw as a duplicate, but it still did not roll out a patch. On August 1, Husain informed the company that she would be making her findings public on August 17.

Google told her that it would be releasing a patch on September 17, but it actually addressed the issue seven hours after its details were made public, 137 days after it learned of its existence.

Written By Eduard Kovacs

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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