Subject: [oss-security] EXIM-Security-2025-12-09.1: Exim 4.99: Remote heap
 corruption
From: Heiko Schlittermann <hs@nodmarc.schlittermann.de>
To: oss-security <oss-security@lists.openwall.com>
Date: Wed, 10 Dec 2025 13:51:13 +0100
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Dear Exim users,

we got reported two possible (related) vulnerabilities in the
latest 4.99 release. From the original report:

,---
| In vulnerable configurations, a remote, unauthenticated attacker can
| achieve heap corruption. I was unable to develop an end-to-end exploit
| chain for remote code execution, but it may be possible with further
| work.
`---

We do not publish any further details yet, until the fix goes public.

While we do not support older versions, please note, that 4.98.1 is not
affected. Other versions might or might not be subject to the same
attack vector.

2025-11-22: we received a report to security@exim.org
2025-11-25: acknowledged the report to the reporter
2025-12-10: this notification

~2025-12-15: publish the fix via the distros repo (accessible for the distro packagers)
~2025-12-18: publish the fix via the default repo (accessible for the public)

Once the fixes passed internal testing, we'll update the schedule and send
another notification about the coordinated release date(s) for distros and
the public.

    Best regards from Dresden/Germany
    Viele Grüße aus Dresden
    Heiko Schlittermann
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