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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.
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In the oss-security post, Exim said the two local privilege-escalation vulnerabilities fixed in 4.99.5 were publicly released on 2026-07-22. The notice also said advance notice had previously been sent to downstream distributors.
Exim maintainers publicly announced the security release and disclosed technical details for the two local privilege-escalation vulnerabilities, including affected versions and upgrade guidance to 4.99.5.
Exim released version 4.99.5 to fix EXIM-Security-2026-06-22.1 and EXIM-Security-2026-06-22.3. The advisory says there is no mitigation for the first issue, while the second can be mitigated by avoiding "force_command" on pipe transports.
Exim's advisory timeline states the maintainers received reports for two vulnerabilities on 2026-06-22: a local directory traversal issue and a command-execution privilege-escalation issue affecting multiple Exim versions.
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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.
Jun 29, 2026
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 disclosed and fixed **CVE-2026-48840**, a pre-authentication information disclosure flaw in Exim’s PROXY protocol handling that affects versions **4.88 through 4.99.3** and is fixed in **4.99.4**. The bug is triggered during SMTP `HELO`/greeting processing when Exim parses a specially crafted **PROXYv2** header with insufficient length, causing uninitialized stack data to be copied into an IP address string and exposed in the SMTP banner. Advisories say the leak can disclose **16 bytes** on `TCPv6` or **4 bytes** on `TCPv4`, including userspace pointers that could help attackers bypass **ASLR** and support further exploitation. The issue affects deployments built with **`SUPPORT_PROXY`** and configured with a non-empty **`hosts_proxy`** value, a combination reported as enabled by default in some downstream builds including Debian, Ubuntu, RHEL EPEL, and Fedora. Exim said exposure is highest where attackers can reach the service from trusted proxy IPs or through a trusted proxy path, and recommended upgrading to **4.99.4**, restricting **`hosts_proxy`** to exact load balancer addresses, or disabling PROXY protocol parsing entirely by unsetting that option. Related downstream advisories were also issued by **cPanel** and **Debian** for packaged Exim deployments.
Jun 29, 2026