NULL Pointer Dereference in HAProxy hpack_dht_insert()
CVE-2026-55204 is a denial-of-service vulnerability affecting HAProxy through version 3.4.0. The flaw is a NULL pointer dereference in hpack_dht_insert() in src/hpack-tbl.c. According to the provided content, the vulnerable code fails to validate the return value of hpack_dht_defrag() when the memory pool is exhausted. Under those conditions, attacker-triggered HPACK dynamic table insertions can lead to dereferencing a NULL pointer, causing HAProxy worker processes to crash.
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