CVE-2026-3549: ECH parsing heap buffer overflow
Vulnerability summary
CVE-2026-3549 is a critical (CVSS 9.8) Heap-based Buffer Overflow vulnerability in wofssl wolfssl. EPSS estimates a 0.50% chance of exploitation in the next 30 days, higher than 42.5% of scored vulnerabilities.
Severe, CVSS 8.3 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Timeline
- 19-03-2026PublishedVulnerability first disclosed.
- 24-03-2026Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
7 scores · 5 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L
- NVDNIST8.3HighCVSS: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
- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · AlpineEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.50%
Chance of exploitation in the next 30 days
Percentile
43%
Versus all other CVEs
30-day change
Decrease -0.06 pp
From 0.55% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Alpine1 product
- wolfssl< 5.9.1-r0 | < 5.9.0-r0
Debian1 product
- wolfsslAll versions (No fix recorded)
Ubuntu1 product
- wolfsslAll versions (No fix recorded)
Wofssl1 product
- wolfssl< 5.9.0
Wolfssl1 product
- wolfssl< 5.9.0
5 vendors · 5 products
