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CVE-2026-55204— HAProxy - NULL Pointer Dereference in hpack_dht_insert Function

Quick assessment

Affected
haproxy haproxy
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

HAProxy是法国HAProxy组织开源的一款开源的TCP/HTTP负载均衡服务器。该服务器提供4层、7层代理,并能支持上万级别的连接,具有高效、稳定等特点。 HAProxy 3.4.0及之前版本存在异常处理不当漏洞，该漏洞源于hpack_dht_insert()函数未能验证内存池耗尽时hpack_dht_defrag()的返回值，可能导致攻击者在内存压力下触发HPACK动态表插入，解引用空指针并崩溃HAProxy工作进程，造成拒绝服务。

CVSS 7.5 · High EPSS 0.48% · P39

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 2

VendorProduct Version RangeStatus
haproxy haproxy ≤ 3.4.0 affected
9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513 unaffected
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I. Basic Information for CVE-2026-55204

Vulnerability Information
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Vulnerability Title
HAProxy - NULL Pointer Dereference in hpack_dht_insert Function
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
空指针解引用
Source: CVE Program / CVE List V5
Vulnerability Title
haproxy 异常处理不当漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
HAProxy是法国HAProxy组织开源的一款开源的TCP/HTTP负载均衡服务器。该服务器提供4层、7层代理,并能支持上万级别的连接,具有高效、稳定等特点。 HAProxy 3.4.0及之前版本存在异常处理不当漏洞，该漏洞源于hpack_dht_insert()函数未能验证内存池耗尽时hpack_dht_defrag()的返回值，可能导致攻击者在内存压力下触发HPACK动态表插入，解引用空指针并崩溃HAProxy工作进程，造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
haproxy haproxy 0 ~ 3.4.0 -

II. Public POCs for CVE-2026-55204

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 10117 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
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POC zip download
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III. Intelligence Information for CVE-2026-55204

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Patches & Fixes for CVE-2026-55204 (1)

Vendor Advisories for CVE-2026-55204 (1)

IV. Related Vulnerabilities

Same product: haproxy
Same vendor: haproxy
Same weakness: CWE-476

V. Comments for CVE-2026-55204

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