CVE-2026-55204
HAProxy - NULL Pointer Dereference in hpack_dht_insert Function
7.5CVSSHIGH
Description
HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in hpack_dht_insert() within src/hpack-tbl.c that fails to validate the return value of hpack_dht_defrag() when the memory pool is exhausted. An attacker can trigger HPACK dynamic table insertions under memory pressure to dereference a NULL pointer and crash HAProxy worker processes, causing denial of service.
CVSS Vector Breakdown
Exploitability
AV:NAttack VectorNetwork
AC:LAttack ComplexityLow
PR:NPrivileges RequiredNone
UI:NUser InteractionNone
Scope
S:UScopeUnchanged
Impact
C:NConfidentialityNone
I:NIntegrityNone
A:HAvailabilityHigh
Weaknesses
Affected Products
Attack Graph
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Exploitability
No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
MITRE ATT&CK
2 techniques Impact
Initial Access
References
Timeline
Published
Jun 18, 2026
Last Updated
Jun 22, 2026
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