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VulnerabilityPublished Updated

CVE-2026-3849: wolfSSL · Out-of-bounds Write

Affects wolfSSLSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium.

Data as of 2 Nov 2026, 10:58 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/V:D/RE:M/U:Amber

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
wolfSSL Inc.wolfSSLAffected
  • >=5.6.0-stable <=5.8.4-stable
Fixed in–
GitHubwolfssl/wolfsslpkg:github/wolfssl/wolfsslOther threatsAffected
  • =5.6.0-stable
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Organizations should immediately audit their use of wolfSSL to determine if ECH is enabled. If ECH is enabled, disable it until a patched version is available. Monitor wolfSSL vendor advisories for patches addressing CVE-2026-3849 and apply updates promptly once released. Implement network-level controls to restrict connections to trusted TLS servers where feasible. Employ runtime protections such as stack canaries and address space layout randomization (ASLR) to mitigate exploitation impact. Conduct thorough testing of wolfSSL integrations with ECH enabled in controlled environments to detect abnormal behavior. For embedded and IoT devices, ensure firmware updates can be deployed quickly to remediate this vulnerability. Additionally, consider using alternative TLS libraries without this vulnerability if immediate patching is not possible. Maintain vigilant monitoring for suspicious TLS handshake anomalies that could indicate exploitation attempts.

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.

References

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