CVE-2026-3549· NVD / CVE Program· CNA wolfSSL

ECH parsing heap buffer overflow

Heap Overflow in TLS 1.3 ECH parsing. An integer underflow existed in ECH extension parsing logic when calculating a buffer length, which resulted in writing beyond the bounds of an allocated buffer. Note that in wolfSSL, ECH is off by default, and the ECH standard is still evolving.

HighCVSS 8.3 · v4.0—No exploit Fix available

Published: Mar 19, 2026
Updated: Jun 17, 2026
EPSS: 0.6% · 44th percentile
CWE: CWE-122

Follow this CVE

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 33 / 40 · 8.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.6%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · wolfSSL: 8.3; 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:L/VI:L/VA:H/SC:L/SI:L/SA:L

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

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Affected systems

Vendor	Product	CPE
wolfssl	wolfssl	cpe:2.3:a:wolfssl:wolfssl

Affected versions

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

wolfssl wolfsslbefore 5.9.0

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.

wofSSL wolfSSL
- before 5.9.0affected · semver

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Debian:12	wolfssl	all versions	—

Same product

wolfssl: all records

Other highest-scoring records for the same primary product.

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
CVE-2024-5991Buffer overread in domain name matching
40Plan
CVE-2020-36177RsaPad_PSS in wolfcrypt/src/rsa.c in wolfSSL before 4.6.0 has an out-of-bounds write for certain relationships between key size and digest s
40Plan
CVE-2014-2898wolfSSL CyaSSL before 2.9.4 allows remote attackers to have unspecified impact via multiple calls to the CyaSSL_read function which triggers
40Plan
CVE-2014-2897The SSL 3 HMAC functionality in wolfSSL CyaSSL 2.5.0 before 2.9.4 does not check the padding length when verification fails, which allows re
40Plan

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
wofSSL wolfSSL	5.9.0	Vendor (CNA)

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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

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

wolfSSL/wolfsslPR 9817

Credits

All researchers

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

Oleh Konko for independently reporting after internal wolfSSL findings and testing wolfSSL's fixother

Variant candidates

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

CVE-2026-526421 days apartDTLS 1.3 ACK heap buffer overflow
33Monitor
CVE-2026-35480 days apartBuffer overflow in CRL number parsing in wolfSSL
28Monitor
CVE-2026-544721 days apartHeap buffer overflow in CertFromX509() via AuthorityKeyIdentifier
25Monitor
CVE-2026-26460 days apartHeap buffer overflow in session parsing with wolfSSL_d2i_SSL_SESSION() function
20Monitor
CVE-2026-518721 days apartHeap Out-of-Bounds Write in DecodeObjectId() in wolfSSL
9Monitor
CVE-2026-544821 days apart1-2 Byte Buffer Overflow in wolfSSL_X509_notAfter/notBefore
9Monitor

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-122 · Heap-based Buffer Overflow

CVSS vector

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