Exim Buffer Overflow Vulnerability

[ Why it matters ]Priority signals

• Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2021-11-03
• Known to be used in ransomware campaigns
• EPSS: 82% chance of exploitation in the next 30 days (higher than 100% of CVEs)
• Critical severity: CVSS 9.8

[ Description ]Official description

An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1. By sending a handcrafted message, a buffer overflow may happen. This can be used to execute code remotely.

CISA: Exim contains a buffer overflow vulnerability in the base64d function part of the SMTP listener that may allow for remote code execution.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 3 May 2022): Apply updates per vendor instructions.

• Patch on git.exim.orgVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD

[ References ]References

• openwall.com/lists/oss-security/2018/02/10/2Mailing ListThird Party Advisory
• packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.htmlExploitThird Party AdvisoryVDB Entry
• www.openwall.com/lists/oss-security/2018/02/07/2Mailing ListThird Party Advisory
• www.securityfocus.com/bid/103049Broken LinkThird Party AdvisoryVDB Entry
• www.securitytracker.com/id/1040461Broken LinkThird Party AdvisoryVDB Entry
• devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-enExploitThird Party Advisory
• exim.org/static/doc/security/CVE-2018-6789.txtVendor Advisory
• git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855f1abecf1Patch
• lists.debian.org/debian-lts-announce/2018/02/msg00009.htmlMailing ListThird Party Advisory
• usn.ubuntu.com/3565-1Third Party Advisory
• www.debian.org/security/2018/dsa-4110Mailing ListThird Party Advisory
• www.exploit-db.com/exploits/44571ExploitThird Party AdvisoryVDB Entry
• www.exploit-db.com/exploits/45671ExploitThird Party AdvisoryVDB Entry
• www.cisa.gov/known-exploited-vulnerabilities-catalogUS Government Resource