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Exim has released version 4.99.2 as a security update to fix four vulnerabilities in the mail transfer agent, tracked as CVE-2026-40684, CVE-2026-40685, CVE-2026-40686, and CVE-2026-40687. The flaws affect specific configurations and stem from unsafe handling of DNS PTR data, corrupt JSON in headers, malformed UTF-8 in headers, and the SPA authenticator when interacting with a hostile or compromised external SPA/NTLM service. Reported impacts include crashes, heap corruption, out-of-bounds reads and writes, and possible heap data leakage, with older Exim branches potentially affected but no longer actively maintained.
One of the disclosed issues, CVE-2026-40684, can crash an Exim connection on systems using musl libc when malformed DNS PTR record data is processed; the same behavior was not reported on glibc systems. Exim said the bug is linked to an octal-printing oddity in musl libc and noted that the issue was raised with the musl maintainer. The fixes were published through Exim's security advisory process and made available in source tarballs and the project's Git repository under the exim-4.99.2 tag.
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6 events from the most recent confirmed update back to the earliest known activity.
Debian published security advisory DSA 6265-1 announcing a security update for exim4 to address the Exim vulnerabilities previously disclosed upstream. This marks downstream distribution remediation for Debian users.
cPanel published a product advisory covering CVE-2026-40684, CVE-2026-40685, CVE-2026-40686, and CVE-2026-40687 affecting Exim. The advisory represents downstream vendor guidance and remediation tracking for cPanel-managed systems.
Solar Designer relayed the Exim 4.99.2 security release and its four associated vulnerabilities to the oss-security mailing list. Follow-up discussion highlighted that CVE-2026-40684 causes crashes on musl libc systems when malformed DNS PTR data is processed, but not on glibc.
The Exim project publicly announced Exim 4.99.2 on the exim-announce list as a security release. This announcement formalized availability of the patched version for users and downstream maintainers.
Exim released version 4.99.2 as a security update to remediate CVE-2026-40684, CVE-2026-40685, CVE-2026-40686, and CVE-2026-40687. The release was made available as source tarballs and in the Exim Git repository under tag exim-4.99.2.
Exim issued security advisory EXIM-Security-2026-04-24 covering four vulnerabilities affecting specific configurations, including issues in DNS PTR handling, JSON header parsing, UTF-8 header processing, and SPA/NTLM authentication. The flaws could cause crashes, out-of-bounds reads or writes, heap corruption, or possible heap data leakage, and older unsupported versions may also be affected.
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Exim maintainers released **Exim 4.99.3** to fix a critical remotely reachable use-after-free flaw in the SMTP server’s **BDAT** body parsing path, tracked as **`CVE-2026-45185`** and referred to as **Dead.Letter**. The vulnerability affects **Exim 4.97 through 4.99.2/4.99.x** when built with **GnuTLS** support and configured to advertise both **`STARTTLS`** and **`CHUNKING`**, and successful exploitation can cause heap corruption with potential remote code execution. Maintainers said Linux distributions received coordinated access to patches ahead of disclosure and urged users to upgrade immediately. According to the advisory and follow-on reporting, the bug is triggered when a client sends a TLS **`close_notify`** before a BDAT transfer finishes and then sends a final cleartext byte over the same TCP connection, leaving Exim in an unsafe state. Exim said there are no effective mitigations short of upgrading, and fixed the issue in **4.99.3** by resetting the input-processing stack when TLS shutdown occurs during an active BDAT transfer. The flaw was reported by **Federico Kirschbaum of XBOW security**, with fuller technical details to be published under **`EXIM-Security-2026-05-01.1`**.
Jun 29, 2026
Exim maintainers released **Exim 4.99.5** to fix two local privilege-escalation vulnerabilities affecting multiple prior versions of the mail transfer agent. According to the security advisory, `EXIM-Security-2026-06-22.1` is a local directory traversal issue affecting Exim **4.88 through 4.99.4** that can let a local user access files outside the spool directory through queue-name transfer command-line arguments, while `EXIM-Security-2026-06-22.3` is a command-execution flaw affecting **4.82 through 4.99.4** in certain `.forward` and pipe transport configurations. The project said there is **no mitigation** for the directory traversal bug short of upgrading, and that the command-execution issue can be reduced by avoiding `force_command` on pipe transports. Release listings and distribution archives show the patched version has been published through Exim's official release channels, and administrators are being urged to update to **4.99.5** to prevent local file access and privilege-escalation risks on affected systems.
Jul 25, 2026
Multiple flaws in the Exim mail transfer agent include **CVE-2023-42115**, a critical unauthenticated remote-code-execution vulnerability rated CVSS 9.8. The out-of-bounds write affects Exim's SMTP service when the `EXTERNAL` authentication scheme is configured and available, potentially enabling an unauthenticated remote attacker to execute code as the Exim service account. Exim versions **4.96.1** and **4.97** address CVE-2023-42115 and the related CVE-2023-42114 and CVE-2023-42116 vulnerabilities. Organizations should upgrade promptly; where immediate patching is not possible, they should disable exposed authentication features and limit remote SMTP access. Other disclosed issues depend on configurations such as SPA/NTLM authentication, an untrusted Proxy Protocol proxy, SPF ACL use, or reliance on an untrusted DNS resolver.
Sep 3, 2026