# CVE-2026-55204: HAProxy - NULL Pointer Dereference in hpack_dht_insert Function > An attacker can crash HAProxy worker processes by triggering a null pointer dereference during HPACK table insertions under memory pressure. - **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 18 Jun 2026 - **Updated:** 14 Jul 2026 - **Also known as:** ALSA-2026:55859, AZL-90261, BIT-haproxy-2026-55204, CLSA-2026-1782820521, CLSA-2026-1782825341, CLSA-2026-1782825734, CLSA-2026-1782825982, CLSA-2026-1782895938, CLSA-2026-1782896085, CLSA-2026-1783527210, CLSA-2026-1784545904, DEBIAN-CVE-2026-55204, GHSA-4vj2-5mvx-3vcc, MINI-4m25-9563-59fx, MINI-7gfj-qvmf-8pf5, MINI-cchh-64mg-m8xg, MINI-jrgw-64h3-pqjq, MINI-vvmx-r2h2-wp8j, MINI-wfjm-jjjq-9f3p, MINI-wfr2-9r47-m97h, RHSA-2026:55859, RHSA-2026:55860, RHSA-2026:55861, RHSA-2026:55862, RLSA-2026:55859, UBUNTU-CVE-2026-55204 ## What is CVE-2026-55204? CVE-2026-55204 is a high-severity vulnerability in haproxy, published on 18 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-476 (NULL Pointer Dereference) ## Which versions are affected by CVE-2026-55204? 1 open source package ship an affected version, including haproxy. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `haproxy` | Bitnami | All versions | 2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1 | | `haproxy` | AlmaLinux:8 | All versions | 1.8.27-5.el8_10.2 | | `haproxy` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.27-5.el8_10.2 | | `haproxy-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.27-5.el8_10.2 | | `haproxy-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.27-5.el8_10.2 | | `haproxy` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.8.27-2.el8_4.2 | | `haproxy-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.8.27-2.el8_4.2 | | `haproxy-debugsource` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.8.27-2.el8_4.2 | | `haproxy` | Red Hat:rhel_aus:8.6::appstream | All versions | 0:1.8.27-4.el8_6.2 | | `haproxy-debuginfo` | Red Hat:rhel_aus:8.6::appstream | All versions | 0:1.8.27-4.el8_6.2 | | `haproxy-debugsource` | Red Hat:rhel_aus:8.6::appstream | All versions | 0:1.8.27-4.el8_6.2 | | `haproxy` | Red Hat:rhel_e4s:8.8::appstream | All versions | 0:1.8.27-5.el8_8.2 | | `haproxy-debuginfo` | Red Hat:rhel_e4s:8.8::appstream | All versions | 0:1.8.27-5.el8_8.2 | | `haproxy-debugsource` | Red Hat:rhel_e4s:8.8::appstream | All versions | 0:1.8.27-5.el8_8.2 | | `haproxy` | Red Hat:rhel_eus_long_life:8.4::appstream | All versions | 0:1.8.27-2.el8_4.2 | | `haproxy-debuginfo` | Red Hat:rhel_eus_long_life:8.4::appstream | All versions | 0:1.8.27-2.el8_4.2 | | `haproxy-debugsource` | Red Hat:rhel_eus_long_life:8.4::appstream | All versions | 0:1.8.27-2.el8_4.2 | | `haproxy` | Red Hat:rhel_eus_long_life:8.6::appstream | All versions | 0:1.8.27-4.el8_6.2 | | `haproxy-debuginfo` | Red Hat:rhel_eus_long_life:8.6::appstream | All versions | 0:1.8.27-4.el8_6.2 | | `haproxy-debugsource` | Red Hat:rhel_eus_long_life:8.6::appstream | All versions | 0:1.8.27-4.el8_6.2 | | `haproxy` | Red Hat:rhel_tus:8.8::appstream | All versions | 0:1.8.27-5.el8_8.2 | | `haproxy-debuginfo` | Red Hat:rhel_tus:8.8::appstream | All versions | 0:1.8.27-5.el8_8.2 | | `haproxy-debugsource` | Red Hat:rhel_tus:8.8::appstream | All versions | 0:1.8.27-5.el8_8.2 | | `haproxy` | Rocky Linux:8 | All versions | 0:1.8.27-5.el8_10.2 | Products: Haproxy Haproxy. ## How do I fix CVE-2026-55204? Upgrade haproxy to a fixed version for your release line: 2.4.36, 2.6.30, 2.8.25 or 3.0.24. ## Is CVE-2026-55204 being exploited? There is no known exploitation of CVE-2026-55204 in the wild and no public exploit code. ## Other vulnerabilities in haproxy - [CVE-2026-55203](https://insights.sbomify.com/CVE-2026-55203/): HAProxy - Integer Overflow in FCGI Demux Record Length Field (critical 9.0) - [CVE-2023-45539](https://insights.sbomify.com/CVE-2023-45539/): Information disclosure in n/a (high 8.2) - [CVE-2024-45506](https://insights.sbomify.com/CVE-2024-45506/): Denial of service in n/a (high 7.5) - [CVE-2023-0836](https://insights.sbomify.com/CVE-2023-0836/): Information disclosure in HAProxy (high 7.5) - [CVE-2019-18277](https://insights.sbomify.com/CVE-2019-18277/): Other in n/a (high 7.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-55204 and fix it if it is affected. What it is: CVE-2026-55204 is a high-severity vulnerability in haproxy, published on 18 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-55204 in the wild and no public exploit code. Affected packages and fixed versions: - haproxy (Bitnami): affected all versions; fixed in 2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-55204/ (Markdown: https://insights.sbomify.com/CVE-2026-55204/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55204 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55204 - OSV: https://osv.dev/vulnerability/CVE-2026-55204 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-55204/ Summaries are generated and may contain mistakes; the official description above is the record.