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CVE-2026-55204

HAProxy - NULL Pointer Dereference in hpack_dht_insert Function

High8.7EPSS 0.48%
Published
Updated
Reserved
Assigned by
VulnCheck

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.

Timeline

  1. ID reserved

    By VulnCheck

  2. · 2 days later

    Published

  3. · 26 days later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-55204, by who scored it
Scored byCVSSScoreVector
VulnCheckCNA (assigner)4.0High8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
VulnCheckCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Analyzed4.0High8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS (exploitation in 30 days)
0.48% · top 58% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.7.

Weakness

Affected products

  • haproxy · haproxy

    • affected ≤ 3.4.0
    • unaffected 9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513

References (2)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .