Use of Uninitialized Variable in Exim - CVE-2026-48840
Published: June 1, 2026
Vulnerability identifier: #VU133143
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-48840
CWE-ID: CWE-457
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Exim
Affected software:
Exim
Exim
Detailed vulnerability description
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to an uninitialized stack memory use in the PROXY-protocol parser when parsing a crafted PROXY version 2 frame with an insufficient payload length. A remote attacker can send a specially crafted PROXY frame to disclose sensitive information.
Only builds compiled with SUPPORT_PROXY and configured with a non-empty hosts_proxy are vulnerable. To reach the vulnerable code, the source IP must match hosts_proxy or the crafted PROXY header must be forwarded through a host already listed in hosts_proxy.
How to mitigate CVE-2026-48840
Install security update from vendor's website.