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01 Record

CVE-2026-73548

Envoy: Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's shared backend pool

HighPUBLISHEDCNA: GitHub_M
CNA base score7.5 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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02 Description

Envoy: Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's shared backend pool

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
0.46% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 39.9% of scored records. A rank, not a probability.
NVD base score
7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD analysis status
Analyzed. NVD last modified this record on 2026-10-05.
Red Hat severity
Important. 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
2026-09-21 19:35Z1 MO AGO
Last updated
2026-09-24 22:35Z1 MO AGO
Reserved
2026-08-12
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
High (CVSS 7.5)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weaknesses
  • CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')Base
Data version
5.2
Document digest
26eadebd6cc9dad4af206dd07973608d5c5684e72dacc0e6a12871cd4ab90000

05 Affected products

VendorProductVersionsPlatforms
envoyproxyenvoy< 1.36.10, >= 1.37.0, < 1.37.6, >= 1.38.0, < 1.38.4, >= 1.39.0, < 1.39.1—

06 References