Loading vulnerability…
CVE-2026-40686 is an out-of-bounds read vulnerability in Exim before version 4.99.2. The issue occurs in configurations that use UTF-8 operators when Exim processes malformed UTF-8 data in message headers, specifically involving large UTF-8 trailing characters. Improper handling of this malformed header input can cause Exim to read memory beyond the intended buffer boundary during header parsing or related string processing. Under certain conditions, the resulting fault can cause data from memory to be incorporated into an error message generated while handling a subsequent unrelated email message on the same connection, creating an information disclosure condition.
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.
9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An Exim information disclosure vulnerability caused by out-of-bounds reads when processing malformed headers with large UTF-8 trailing characters.
A vulnerability in Exim caused by improper handling of specially crafted UTF-8 input and line folding, potentially leading to incorrect processing.
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.