How severe is CVE-2026-3547?

CVE-2026-3547 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-3547 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3547?

CVE-2026-3547 affects Wolfssl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-3547?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-3547 have an EU (EUVD) identifier?

Yes. CVE-2026-3547 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13166.

When was CVE-2026-3547 published?

CVE-2026-3547 was published on 2026-03-19 and last updated on 2026-06-17.

CVE-2026-3547

CVE-2026-3547 is a high-severity vulnerability in Wolfssl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-125.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13166
Weakness: CWE-125
Affected product: Wolfssl
Published: 2026-03-19
Last modified: 2026-06-17

Description

Out-of-bounds read in ALPN parsing due to incomplete validation. wolfSSL 5.8.4 and earlier contained an out-of-bounds read in ALPN handling when built with ALPN enabled (HAVE_ALPN / --enable-alpn). A crafted ALPN protocol list could trigger an out-of-bounds read, leading to a potential process crash (denial of service). Note that ALPN is disabled by default, but is enabled for these 3rd party compatibility features: enable-apachehttpd, enable-bind, enable-curl, enable-haproxy, enable-hitch, enable-lighty, enable-jni, enable-nginx, enable-quic.

Frequently asked questions

What is CVE-2026-3547?: Out-of-bounds read in ALPN parsing due to incomplete validation. wolfSSL 5.8.4 and earlier contained an out-of-bounds read in ALPN handling when built with ALPN enabled (HAVE_ALPN / --enable-alpn). A crafted ALPN protocol list could trigger an out-of-bounds read, leading to a potential process crash (denial of service). Note that ALPN is disabled by default, but is enabled for these 3rd party compatibility features: enable-apachehttpd, enable-bind, enable-curl, enable-haproxy, enable-hitch, enable-lighty, enable-jni, enable-nginx, enable-quic.
How severe is CVE-2026-3547?: CVE-2026-3547 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-3547 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3547?: CVE-2026-3547 affects Wolfssl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-3547?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-3547 have an EU (EUVD) identifier?: Yes. CVE-2026-3547 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13166.
When was CVE-2026-3547 published?: CVE-2026-3547 was published on 2026-03-19 and last updated on 2026-06-17.

References

https://github.com/wolfSSL/wolfssl/pull/9859

Affected products (1)

cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*

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