CVE-2026-33555An issue was discovered in HAProxy before 3.3.6.
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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An issue was discovered in HAProxy before 3.3.6. The HTTP/3 parser does not check that the received body length matches a previously announced content-length when the stream is closed via a frame with an empty payload. This can cause desynchronization issues with the backend server and could be used for request smuggling. The earliest affected version is 2.6.
- CVSS
- 4.0 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
- Weakness (CWE)
- CWE-130
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mitre
- NVD analysis
- Modified
- Record last updated
- Oct 18, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
HAProxy HAProxy haproxy:haproxy (from the name) | from 2.6 before 3.3.6 | CNA record |
haproxy haproxy haproxy:haproxy | from 2.6.0 before 3.3.6 | NVD |
References
- https://www.haproxy.orgproduct
- https://www.haproxy.com/documentation/haproxy-aloha/changelog/release-notes
- https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84patch
- https://www.mail-archive.com/haproxy@formilux.org/msg46752.htmlrelease-notes
- https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.htmlexploit, third-party-advisory
- https://lists.debian.org/debian-lts-announce/2026/10/msg00036.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.