VulnerabilityPublished 25 Jun 2026Updated 17 Oct 2026

CVE-2026-55964: Wolfssl · Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA

Affects wolfsslSource GCVE Database

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Not known to be exploited · CVSS 5.3 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-68g3-7fhp-7rg3

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10wolfssl`pkg:deb/ubuntu/wolfssl?arch=source&distro=stonking`Other threats	Affected =5.9.1-0.1 =5.9.2-1	Fixed in–
Ubuntu 26.04 LTSwolfssl`pkg:deb/ubuntu/wolfssl?arch=source&distro=resolute`Other threats	Affected 5.7.2-0.1 – 5.9.1-0.1 4 affected builds	Fixed in–
Ubuntu 25.10wolfssl`pkg:deb/ubuntu/wolfssl?arch=source&distro=questing`Other threats	Affected =5.7.2-0.1	Fixed in–
Ubuntu 24.04 LTSwolfssl`pkg:deb/ubuntu/wolfssl?arch=source&distro=noble`Other threats	Affected 5.5.4-2 – 5.6.6-1.3build1 6 affected builds	Fixed in–
Ubuntu 22.04 LTSwolfssl`pkg:deb/ubuntu/wolfssl?arch=source&distro=jammy`Other threats	Affected 4.6.0-3 – 5.2.0-2 5 affected builds	Fixed in–
Ubuntu 20.04 LTSwolfssl`pkg:deb/ubuntu/wolfssl?arch=source&distro=focal`Other threats	Affected 4.1.0+dfsg-2 – 4.3.0+dfsg-2 5 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should monitor vendor advisories for updates. Since the issue affects only the OpenSSL-compatible path and not native verification, avoiding reliance on the OpenSSL-compatible path may reduce risk. No specific mitigations are documented at this time.

Description

A vulnerability in wolfSSL's OpenSSL-compatible certificate path building allows intermediate CA certificates marked as CA:TRUE but lacking the keyCertSign usage to be incorrectly accepted as signing CAs. This affects only the OpenSSL-compatibility path and not native certificate verification. No known exploits or patches are currently available.

Impact

The vulnerability could allow an attacker to use intermediate CA certificates without the proper keyCertSign usage to be accepted as signing CAs in the OpenSSL-compatible verification path, potentially undermining certificate validation integrity. However, there are no known exploits in the wild and no direct confidentiality or availability impact is indicated. The CVSS score is 5.3 (medium severity), reflecting limited impact primarily on integrity.

Summary

CVE-2026-55964 describes a flaw in certain wolfSSL builds where intermediate CA certificates that have the CA:TRUE flag but do not include the keyCertSign key usage are mistakenly accepted as valid signing CAs during OpenSSL-compatible certificate path building. This improper acceptance occurs because the check was previously exempt for chain-supplied temporary CAs but is now enforced except for operator-loaded root certificates and self-signed roots.

CWE-295Improper Certificate Validation (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not validate, or incorrectly validates, a certificate.
Architecture and Design · Implementation
Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
Implementation
If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
OWASP Cheat Sheets
Transport Layer Protection (opens in a new tab)
TLS Cipher String (opens in a new tab)
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V9.2.1 (opens in a new tab)
V1.9.2 (opens in a new tab)
V2.8.5 (opens in a new tab)
Attack patterns
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 18 Oct 2026, 04:48 UTC

WeaknessesCWE-295

Technical details

References

Community reviews

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