9.8

CVE-2026-3849: Buffer Overflow in HPKE via Oversized ECH Config

Analyzed
AliasesUBUNTU-CVE-2026-3849DEBIAN-CVE-2026-3849ALPINE-CVE-2026-3849
Published 19-03-2026Last modified 25-03-2026

Vulnerability summary

CVE-2026-3849 is a critical (CVSS 9.8) Out-of-bounds Write vulnerability in wolfssl inc. wolfssl. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 39.2% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 6.9, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
9.8/10
010
Critical · v3.1 (NVD)
EPSS score
0.45%
0%100%
Low · -0.31 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 19-03-2026
    PublishedVulnerability first disclosed.
  2. 25-03-2026
    Last modifiedVulnerability information updated.

Description

Stack Buffer Overflow in wc_HpkeLabeledExtract via Oversized ECH Config. A vulnerability existed in wolfSSL 5.8.4 ECH (Encrypted Client Hello) support, where a maliciously crafted ECH config could cause a stack buffer overflow on the client side, leading to potential remote execution and client program crash. This could be exploited by a malicious TLS server supporting ECH. Note that ECH is off by default, and is only enabled with enable-ech.

CVSS metrics

7 scores · 5 sources · 2 versions

EPSS trend

Probability

0.45%

Chance of exploitation in the next 30 days

Percentile

39%

Versus all other CVEs

30-day change

Decrease -0.31 pp

From 0.77% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Alpine1 product
  • wolfssl≥ 5.6.0, < 5.9.1-r0 | ≥ 5.6.0, < 5.9.0-r0
Debian1 product
  • wolfsslAll versions (No fix recorded)
Ubuntu1 product
  • wolfsslAll versions (No fix recorded)
Wolfssl1 product
Wolfssl inc.1 product
  • wolfssl≥ v5.6.0-stable, ≤ v5.8.4-stable

5 vendors · 5 products

References

5 links