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01 Record

CVE-2026-55602

http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass

MediumPUBLISHEDCNA: GitHub_M
CNA base score6.9 CVSS v4.0CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

02 Description

http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass

03 Exploitation and scoring

Exploitation
Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
SSVC decision
  • ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.37% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 31.4% of scored records. A rank, not a probability.
NVD base score
6.9 (CVSS v4.0), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/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
NVD analysis status
Analyzed. NVD last modified this record on 2026-10-25.
Red Hat severity
Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-06-22 15:58Z4 MO AGO
Last updated
2026-06-23 14:18Z4 MO AGO
Reserved
2026-06-16
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
Medium (CVSS 6.9)
CNA CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Weaknesses
  • CWE-20Improper Input ValidationClass
  • CWE-187Partial String ComparisonVariant
  • CWE-346Origin Validation ErrorClass
Data version
5.2
Document digest
26ce84940689487cb8c261754deb64226de6b3609abf2f500cb21d21f9bce187

05 Affected products

VendorProductVersionsPlatforms
chimuraihttp-proxy-middleware>= 4.0.0, < 4.1.0, >= 3.0.0, < 3.0.6, >= 0.16.0, < 2.0.10—

06 References