Unbounded HSS public key level count allows huge array allocation during signature verification
Published Oct 2, 2026 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
Unbounded HSS public key level count allows huge array allocation during signature verification
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker who can supply both an HSS public key and a signature to cause a denial of service through memory exhaustion via a public key encoding with an excessive level count, because the level count L read when parsing an HSS public key was not checked against the RFC 8554 maximum of 8, and signature parsing then allocated an array of L - 1 entries before reading any further signature data. A single verification can commit up to about 17 GB of memory or fail with an OutOfMemoryException.
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- LOW
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published Oct 2, 2026 · Last refreshed Nov 3, 2026