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CVE-2026-3593 is a heap use-after-free vulnerability in ISC BIND 9's DNS-over-HTTPS implementation. The flaw occurs in HTTP/2 handling when SETTINGS frames modify INITIAL_WINDOW_SIZE while a DNS-over-HTTPS response is still pending. In the vulnerable code path, server_read_callback in lib/isc/netmgr/http.c reads from the HTTP/2 socket write buffer after the underlying memory has already been released by the write callback and network handle teardown logic. This leaves a dangling buffer reference that can be accessed during subsequent HTTP/2 flow-control processing, resulting in a use-after-free read and memory corruption condition. Affected versions are BIND 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9.18.x is explicitly not affected.
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20 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A use-after-free vulnerability in ISC BIND 9 DNS-over-HTTPS handling that can trigger denial of service on hardened/ASAN builds when HTTP/2 SETTINGS frames cause nghttp2 to re-read a freed response buffer.
A heap use-after-free vulnerability in ISC BIND 9 DNS-over-HTTPS (DoH) implementation that can cause memory corruption, crashes, and potentially arbitrary code execution.
A use-after-free memory corruption vulnerability in BIND 9 DNS-over-HTTPS handling that can be triggered by malicious HTTP/2 traffic against secure endpoints.
A heap use-after-free vulnerability in the BIND 9 DNS-over-HTTPS implementation.
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.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.