Exim 4.100.1 Security Update: Fix 4 Remote Vulns (OOB Write, UAF, Uninit Data, SMTP Smuggling)

Key Information Summary of Exim 4.100.1 Security Update Vulnerability Overview The Exim maintainers have released version 4.100.1, which fixes 4 security vulnerabilities (corresponding to 4 security advisories): Scope of Impact Affected Versions: Exim 4.83 (2014) through 4.100 (inclusive). Trigger Conditions: - 12.1 / 12.3: Requires Proxy-Protocol support to be enabled at install time, and a proxy must be configured (the proxy must be in a buggy or compromised state). - 12.2: Requires guile 4.0 or higher to be enabled at install time, configured to accept TLS-on-connect; the option must be enabled (which is not the default setting). - 12.4: All Exim versions are affected (no special configuration required). Impact of Attack: - 12.1: A remote attacker can cause an out-of-bounds write of up to 239 bytes, potentially leading to heap corruption. - 12.2: A remote attacker can trigger a use-after-free condition, potentially causing the reception process to crash. - 12.3: A remote attacker can lead to stack data leakage. - 12.4: A remote attacker can cause a discrepancy between sent and received messages (SMTP smuggling). Fix Details Fixed Version: All 4 vulnerabilities are fixed in Exim 4.100.1; upgrading is strongly recommended for affected users. Specific Fix for Each Vulnerability: - 12.1: The fix ensures that data reads are properly sized (properly sizes a data read). - 12.2: The fix changes the control flow to avoid the problematic data usage (changes the control flow to avoid the data use). - 12.3: The fix repeats reads until a complete protocol header is received (repeats reads until a complete protocol header is received). - 12.4: The fix properly identifies the end of the data phase, specifically for a rejection (properly identifies the end of data phase, for a rejection). Mitigation Measures: - 12.1 / 12.3: None. - 12.2: Disable the feature option. - 12.4: None. POC / Exploit Code The page does not contain POC or exploit code blocks.

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Exim 4.100.1 Security Update: Fix 4 Remote Vulns (OOB Write, UAF, Uninit Data, SMTP Smuggling)