CVE-2026-33555 Details
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.
View at NVD
Exploit prediction scoring system (EPSS) score for CVE-2026-33555
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.3 Probability of exploitation activity being observed over the next 30 days (22st percentile)
CVSS score for CVE-2026-33555
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
4 Medium
Products affected by CVE-2026-33555
Haproxy 3.0.12
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Low
More on DVE scores

CVE-2026-33555 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
US 71 36.60%
DE 28 14.43%
AU 12 6.19%
NL 12 6.19%
SG 10 5.15%
ID 9 4.64%
FR 7 3.61%
RU 6 3.09%
IT 4 2.06%
CA 4 2.06%

Is CVE-2026-33555 part of your extended attack surface? Bitsight helps security leaders rapidly identify exposure and detect threats in order to prioritize, communicate, and mitigate risk.

View interactive product tours

CVE-2026-33555 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Technology 125 85.03%
Telecommunications 17 11.56%
Education 3 2.04%
Business Services 2 1.36%

Bitsight Data Discovery and Continuous Threat Scanning

Bitsight, the leading provider in Cyber Risk Management, introduced the next-generation internet scanner Bitsight Groma in May 2024. This technology continuously scans the entire internet to discover assets, collect asset attribution evidence, and identify an ever-growing set of security observations, such as vulnerabilities and misconfigurations. Groma’s scanning activities presently encompass:


  • 40 million-plus monitored organizations
  • 250 million-plus host names
  • 4 billion-plus routable IPv4 and IPv6 addresses

Greynoise’s recent study testifies the speed of Bitsight Groma.

Learn more about Bitsight Groma
Bitsight data discovery
Governance charcoal background

How we use Bitsight Groma data 

Empower Security Research

Bitsight TRACE team investigates security incidents and identifies vulnerabilities and threats.

View latest security research 

See Your External Attack Surface

See what you’re up against across the expanding attack surface. Prioritize what matters most. And mitigate where you’re most vulnerable.

External Attack Surface Management