Bug 2541849 (CVE-2026-100701)

Summary: CVE-2026-100701 nodemailer: nodemailer: Information disclosure via TLS servername cache confusion
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abarbaro, alizardo, dschmidt, ikhan, jchui, jhe, jlanda, kaycoth, kshier, ktsao, lchilton, nboldt, oaljalju, psrna, rbobbitt, rhel-process-autobot, sfeifer, simaishi, stcannon, watson-tool-maintainers, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in nodemailer. In multi-tenant environments, a remote attacker can exploit a cache confusion vulnerability by priming the shared Domain Name System (DNS) cache with a custom Transport Layer Security (TLS) server name. Because cached entries overwrite subsequent connection configurations for the same host, the client sends an incorrect Server Name Indication (SNI) and validates the peer certificate against an attacker-controlled identity. This flaw leads to information disclosure, allowing the attacker to intercept mail traffic and capture sensitive Simple Mail Transfer Protocol (SMTP) credentials.
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Description OSIDB Bzimport 2026-09-26 13:35:35 UTC 
Nodemailer versions 5.0.0 through 10.0.1 use a process-global DNS cache that is keyed only by the DNS host, while each cache entry also stores the caller-specific TLS servername. When two direct TLS/SMTPS transports (secure: true) resolve the same non-IP host with different tls.servername values, the first transport's servername is returned on the cache hit and overwrites the second transport's explicitly configured value, so Nodemailer sends the wrong SNI value and validates the peer certificate against the wrong identity. In multi-tenant services or SNI-routed SMTP gateways, an attacker who can prime the cache can cause a victim transport to connect to the attacker's TLS virtual host and accept the attacker's certificate even with rejectUnauthorized: true, disclosing the victim's SMTP credentials. Fixed in 10.0.2.