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01 Record

CVE-2026-54556

Http4s: HTTP/2 Denial of Service with Ember Backend

HighPUBLISHEDCNA: GitHub_M
CNA base score8.2 CVSS v4.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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02 Description

Http4s: HTTP/2 Denial of Service with Ember Backend

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • 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
0.52% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 44.1% of scored records. A rank, not a probability.
NVD base score
8.2 (CVSS v4.0), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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
Deferred. NVD last modified this record on 2026-09-09.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

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
2026-08-26 14:10Z2 MO AGO
Last updated
2026-08-29 02:38Z2 MO AGO
Reserved
2026-06-15
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
High (CVSS 8.2)
CNA CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weaknesses
  • CWE-409Improper Handling of Highly Compressed Data (Data Amplification)Base
Data version
5.2
Document digest
8cc82f6a5d6ac9c4e5eec33041f9e358db95bc536d2dddcd51dceb7dd7ec5ef7

05 Affected products

VendorProductVersionsPlatforms
http4shttp4s< 0.23.35, >= 1.0.0-M1, < 1.0.0-M46—
org.http4shttp4s-ember-core_2.12< 0.23.35—
org.http4shttp4s-ember-core_2.13>= 1.0.0-M1, < 1.0.0-M46, < 0.23.35—
org.http4shttp4s-ember-core_3>= 1.0.0-M1, < 1.0.0-M46, < 0.23.35—

06 References