High severity · published Jun 18, 2026
CVE-2026-55204
HAProxy - NULL Pointer Dereference in hpack_dht_insert Function
7.5
CVSS
0.5%
EPSS
No
On KEV
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
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 41% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HA
haproxy · haproxy
through 3.4.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55204
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55204
Patch
https://github.com/haproxy/haproxy/commit/9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513
Third Party Advisory
https://www.vulncheck.com/advisories/haproxy-null-pointer-dereference-in-hpack-dht-insert-function
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