VulnerabilityAnalyzed
CVE-2026-33555
An issue was discovered in HAProxy before 3.3.6.
MEDIUM 5.8EPSS 0.30%
Does this matter?
Lower severity and a low EPSS score (0.30%). Track it; it rarely justifies an emergency change on its own.
Description
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 3.1
- 5.8 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
- EPSS
- 0.30% probability · 22th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-130
- Affected
- haproxy/haproxy
- Source
- cve@mitre.org
References
- https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84Patch
- https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.htmlExploit, Third Party Advisory
- https://www.haproxy.com/documentation/haproxy-aloha/changelog/Release Notes
- https://www.haproxy.orgProduct
- 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.