CVE-2026-5466

Signature forgery via unchecked ECCSI scalars

Published Apr 10, 2026 · Updated Apr 10, 2026

Improper ECCSI verification in wolfSSL before 5.9.1 allows attackers to forge signatures for any message or identity via zero-valued scalars. wc_VerifyEccsiHash decodes r and s without enforcing the valid range, so s=0 produces the point at infinity and r=0 makes the final comparison succeed. Reachability requires ECCSI support and an attacker-controlled signature; exploitation defeats signature authenticity and integrity without directly exposing data or interrupting service.

CVSS severity7.6
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper ECCSI verification in wolfSSL before 5.9.1 allows attackers to forge signatures for any message or identity via zero-valued scalars. wc_VerifyEccsiHash decodes r and s without enforcing the valid range, so s=0 produces the point at infinity and r=0 makes the final comparison succeed. Reachability requires ECCSI support and an attacker-controlled signature; exploitation defeats signature authenticity and integrity without directly exposing data or interrupting service.

The record

CVE
CVE-2026-5466
Published
Apr 10, 2026
Updated
Apr 10, 2026
Vendor
wolfSSL
Product
wolfSSL
Classifications
CWE-347, T1553
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.9.1

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

wolfSSL · wolfSSLversion=0 <5.9.1

Published CVSS scores

8.1NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
7.6wolfSSL Inc.CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1553Subvert Trust Controls

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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