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01 Record

CVE-2026-103603

Unbounded HSS public key level count allows huge array allocation during signature verification

HighPUBLISHEDCNA: bcorg
CNA base score8.7 CVSS v4.0CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

02 Description

Unbounded HSS public key level count allows huge array allocation during signature verification

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
0.50% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 42.7% of scored records. A rank, not a probability.
NVD base score
8.7 (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: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
Analyzed. NVD last modified this record on 2026-10-28.
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
2026-10-02 07:10Z27 DAYS AGO
Last updated
2026-10-02 17:44Z26 DAYS AGO
Reserved
2026-09-30
Assigning CNA
bcorg
Record state
PUBLISHED
Severity
High (CVSS 8.7)
CNA CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weaknesses
  • CWE-789Memory Allocation with Excessive Size ValueVariant
Data version
5.2
Document digest
730a00d0a474377a9f845023f662801dfeb18784e3de6b6c7279f7d1af3f6a29

05 Affected products

VendorProductVersionsPlatforms
Legion of the Bouncy Castle Inc.bc-csharp0 to < 2.7.0—

06 References