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NVD / CVE Program· CNA wolfSSL

CVE-2026-55964: Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA (temporary CA exemption)

Noroxi assessment

Priority: Monitor (action score 25/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: wolfssl (Alpine:v3.24) 5.9.2-r0.

Low priority for now. Upgrade to wolfssl (Alpine:v3.24) 5.9.2-r0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA. Intermediate CA certificates are required to have the keyCertSign key usage when a Key Usage extension is present, but chain-supplied temporary CAs (WOLFSSL_TEMP_CA) added while building a certificate path were previously exempted from this check, so an intermediate asserting CA:TRUE but lacking keyCertSign was accepted as a signing CA. The check now applies to chain-supplied temporary CAs as well; only operator-loaded root certificates (WOLFSSL_USER_CA) and self-signed roots remain exempt. Per RFC 5280 an absent Key Usage extension implies all usages, so the requirement is enforced only when the extension is actually present (extKeyUsageSet). Affects the OpenSSL-compatibility certificate-path-building path (X509_verify_cert / X509_STORE, OPENSSL_EXTRA/OPENSSL_ALL), where untrusted chain intermediates are added as temporary CAs; native (non-OpenSSL-compat) certificate verification does not create temporary CAs and is unaffected. Within those builds, the check applies unless ALLOW_INVALID_CERTSIGN is defined.

MediumCVSS 6.3 · v4.0—No exploit Fix available
Published
Jun 25, 2026
Updated
Jun 26, 2026
EPSS
0.1% · 8th percentile

Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
25 / 40 · 6.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · wolfSSL
6.3
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-55964

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
wolfsslwolfssl

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • wolfssl wolfssl5.7.4 and later · before 5.9.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (wolfSSL). Independent of NVD's CPE analysis and usually ahead of it.

  • wolfSSL wolfSSL

    • 5.7.4 and later · up to and including 5.9.1affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.24wolfsslfrom 5.7.4 · before 5.9.2-r05.9.2-r0
Debian:12wolfsslfrom 0—

Same product

wolfssl: all records

Other highest-scoring records for the same primary product.

  • CVE-2017-13099wolfSSL Bleichenbacher/ROBOT
    60This week
  • CVE-2019-11873wolfSSL 4.0.0 has a Buffer Overflow in DoPreSharedKeys in tls13.c when a current identity size is greater than a client identity size.
    42Plan
  • CVE-2017-2800A specially crafted x509 certificate can cause a single out of bounds byte overwrite in wolfSSL through 3.10.2 resulting in potential certif
    42Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-55958Jun 25, 2026 · Renesas TSIP TLS 1.3 transcript buffer out-of-bounds write in tsip_StoreMessage
    33Monitor
  • ← EarlierCVE-2026-55960Jun 25, 2026 · Un-negotiated Raw Public Key (RFC 7250) accepted in place of X.509, bypassing chain validation
    32Monitor
  • Later →CVE-2026-7531Jun 25, 2026 · Use-after-free in PQC hybrid key-share handling
    9Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:wolfssl5.9.2-r0 · Alpine:v3.24Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-519477 days apartwolfSSL ECDSA Certificate Verification
    37Monitor
  • CVE-2025-7395342 days apartDomain Name Validation Bypass with Apple Native Certificate Validation
    36Monitor
  • CVE-2026-113100 days apartX.509 trust-chain bypass in wolfSSL_X509_verify_cert() via untrusted intermediate anchoring
    34Monitor
  • CVE-2026-550176 days apartImproper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates
    34Monitor
  • CVE-2026-8910294 days apartOCSP stapling v2 multi accepts non-CA chain certificates as issuers
    33Monitor
  • CVE-2026-9330294 days apartTrusted peer certificate match ignores public key, allowing forged CA clones
    33Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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-secondary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin
override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {  // Left empty for the test environment}

Fixed

kotlin
val client = OkHttpClient.Builder()  .certificatePinner(    CertificatePinner.Builder()      .add("api.sirius.example", "sha256/…")      .build()  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records