CVE-2026-55204: haproxy NULL Pointer Dereference
CVSS: 8.7v4.0HighAnalyzed
AliasesRHSA-2026:55859RHSA-2026:55860RHSA-2026:55861RHSA-2026:55862UBUNTU-CVE-2026-55204DEBIAN-CVE-2026-55204CGA-59pj-prwm-qcw7CGA-694q-gc8x-55gjCGA-jc64-72hv-p256CGA-v744-7mqp-96j4CGA-63c8-cw58-3fjmCGA-66hg-g5c2-vmhrCGA-7gm8-7qrc-j4j3CGA-7h24-x2hj-rgcqCGA-fqjh-cr5p-2q86CGA-h82c-82pj-f3mxCGA-rh8p-g38x-2r7cCGA-vfxw-7r5j-fg79CGA-vx6j-cj6p-m98pCGA-xh9g-v483-4cc3
Published 18-06-2026Last modified 14-07-2026
Vulnerability summary
CVE-2026-55204 is a high (CVSS 8.7) NULL Pointer Dereference vulnerability in haproxy. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 40.6% of scored vulnerabilities.
CVSS score
8.7/10
010
High · v4.0 (CVE.org)EPSS score
0.48%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 17 · Related 11MGASA-2026-0250OPENSUSE-SU-2026:11090-1OPENSUSE-SU-2026:21245-1RHSA-2026:35453RHSA-2026:55679RHSA-2026:55772RHSA-2026:55800RHSA-2026:55801RHSA-2026:55802RHSA-2026:55803SUSE-SU-2026:22515-1SUSE-SU-2026:22544-1SUSE-SU-2026:22557-1SUSE-SU-2026:22587-1SUSE-SU-2026:22663-1SUSE-SU-2026:2651-1SUSE-SU-2026:2652-1CGA-28JH-WW24-VMMHUSN-8459-1
Timeline
- 18-06-2026PublishedVulnerability first disclosed.
- 14-07-2026Last modifiedVulnerability information updated.
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 metrics
10 scores · 7 sources · 2 versionsHigh 8.7Preferred score · CVE.org (CNA)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NSourcesAll 6 agree
- OSV · UbuntuEcosystem advisory · calculated8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated8.7HighCVSS: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
- OSV · WolfiEcosystem advisory · calculated8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- OSV · ChainguardEcosystem advisory · calculated8.7HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- NVDNIST8.7HighCVSS: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
High 7.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSourcesAll 4 agree
- OSV · Red hatEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.48%
Chance of exploitation in the next 30 days
Percentile
41%
Versus all other CVEs
30-day change
0.00 pp
From 0.48% on 21-09-2026
21-09-202621-10-2026
EPSS score0.48%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Chainguard7 products
- haproxy-2.4< 2.4.36-r0
- haproxy-2.6< 2.6.31-r0
- haproxy-2.8< 2.8.26-r0
- haproxy-3.0< 3.0.24-r0
- haproxy-3.1All versions (No fix recorded)
Redhat3 products
- haproxy< 0:1.8.27-5.el8_10.2 | < 0:1.8.27-5.el8_8.2 | < 0:1.8.27-2.el8_4.2 | < 0:1.8.27-4.el8_6.2
- haproxy-debuginfo< 0:1.8.27-5.el8_10.2 | < 0:1.8.27-5.el8_8.2 | < 0:1.8.27-2.el8_4.2 | < 0:1.8.27-4.el8_6.2
- haproxy-debugsource< 0:1.8.27-5.el8_10.2 | < 0:1.8.27-5.el8_8.2 | < 0:1.8.27-2.el8_4.2 | < 0:1.8.27-4.el8_6.2
Wolfi2 products
- haproxy-3.2< 3.2.20-r0
- haproxy-3.3< 3.3.11-r0
Debian1 product
- haproxyAll versions (No fix recorded) | < 3.2.20-1
Haproxy1 product
- haproxy≤ 3.4.0 | < 2.4.36 | ≥ 2.5, < 2.6.30 | ≥ 2.7, < 2.8.25 | ≥ 2.9, < 3.0.24 | ≥ 3.1, < 3.2.20 | ≥ 3.3, < 3.4.1
Ubuntu1 product
- haproxyAll versions (No fix recorded) | < 2.4.30-0ubuntu0.22.04.2 | < 2.8.16-0ubuntu0.24.04.3 | < 3.0.12-0ubuntu0.25.10.5 | < 3.2.9-1ubuntu2.2
6 vendors · 15 products
References
20 links- www.vulncheck.com/advisories/haproxy-null-pointer-dereference-in-hpack-dht-insert-functionThird Party AdvisoryARTICLEAdvisory
Show all 20 references
- github.com/haproxy/haproxyPACKAGE