Loading vulnerability…
CVE-2026-48840 is a pre-authentication information disclosure vulnerability in Exim’s PROXY protocol parser affecting Exim 4.88 through 4.99.3, fixed in 4.99.4. In the vulnerable code path, Exim’s proxy_protocol() function uses an uninitialized stack union for PROXYv2 header/address parsing and validates only that the supplied frame does not exceed the union size, without enforcing the minimum payload length required for the claimed address family. A malformed PROXYv2 frame with a too-short declared payload length can therefore leave address fields uninitialized. When the frame claims TCP over IPv6 (family 0x21), Exim can copy 16 bytes of uninitialized stack data from the IPv6 source-address field; similarly, a short TCPv4 frame (family 0x11) can leak 4 bytes. Exim then formats the uninitialized bytes as an IP address string and exposes them to the client during SMTP greeting/Hello handling. The issue is reachable before authentication and only affects deployments compiled with SUPPORT_PROXY and configured with a non-empty hosts_proxy.
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
14 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A long-standing Exim vulnerability affecting the SMTP service, reachable pre-authentication and tied to IPv6/SMTP Hello handling in builds using hosts_proxy with SUPPORT_PROXY enabled.
An information disclosure vulnerability in Exim affecting SMTP handling when PROXY protocol support is enabled, allowing leakage of up to 16 bytes of uninitialized memory and potentially weakening protections such as ASLR.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.