CVE-2026-48840 Information disclosure in Exim

Medium 5.3 Published 30 May 2026 Updated 5 Jun 2026

Attackers can read uninitialized stack memory from Exim mail servers in specific proxy configurations, potentially exposing sensitive data.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-48840?

CVE-2026-48840 is a medium-severity vulnerability in Exim Exim, published on 30 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

Weakness: CWE-839

Which versions are affected by CVE-2026-48840?

It affects 1 product.

Products include Exim Exim.

How do I fix CVE-2026-48840?

Upgrade to a fixed version.

Is CVE-2026-48840 being exploited?

There is no known exploitation of CVE-2026-48840 in the wild and no public exploit code.

All Exim Exim vulnerabilities

Sources

Also known as DEBIAN-CVE-2026-48840, GHSA-wgrp-2w9f-fmvg, UBUNTU-CVE-2026-48840, USN-8353-1.