CVE-2026-3547

HIGH 7.5 ALL-YEARS

Published 2026-03-19 · Last modified 2026-03-21 · wolfSSL · NVD: Analyzed

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.

ELEVATED IMPACT

Severe if exploited (CVSS 7.5), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.3%chance of exploitation in 30 days · 21st percentile

○ In CISA KEV○ Catalogued PoC◆ SSVC: exploitation none, automatable yes

Impact if exploited

7.5CVSS 3.1 · HIGH · CNA

ConfidentialityNone
IntegrityNone
AvailabilityHigh

What an attacker needs

✓Access: Reachable over the network — no local access needed
✓Privileges: No account or privileges required
✓User interaction: No user interaction needed
✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

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Affected

Vendors Wolfssl

Products Wolfssl

Weakness (CWE)

CWE-125: : out-of-bounds read

CVSS vector

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

References and research data (JSON)

Known Affected Software Configurations

Vendor	Product	Version range
Wolfssl	Wolfssl	< 5.9.0

All CVSS metrics

HIGH 7.5 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
HIGH 7.5 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Patches & mitigations

https://github.com/wolfSSL/wolfssl/pull/9859 patchIssue TrackingPatchCVE record · wolfSSL · Updated 2026-03-19T20:20:42.608Z
NVD · CVE-2026-3547 · Updated 2026-06-17T10:43:45.970

Advisories

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-13166 ADVISORYEUVD · EUVD-2026-13166

Sources: NVD · CVE.org · All sources and attribution · EPSS