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No exploitation reportedFix available

CVE-2019-18840

No exploitation reported by the sources we read.

  • Published2019-11-09
  • WeaknessCWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In wolfSSL 4.1.0 through 4.2.0c, there are missing sanity checks of memory accesses in parsing ASN.1 certificate data while handshaking. Specifically, there is a one-byte heap-based buffer overflow inside the DecodedCert structure in GetName in wolfcrypt/src/asn.c because the domain name location index is mishandled. Because a pointer is overwritten, there is an invalid free.

Timeline

dates in UTC
  1. 2019-11-0913:15CVE publishedNVD

Versions per branch

NVD
Wolfssl
BranchAffectedFixed in
4.x≥ 4.1.0, ≤ 4.2.0cno fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • wolfsslUbuntu:20.04:LTSall versions · fixed in 4.2.0+dfsg-3
  • wolfsslDebian:13all versions · fixed in 4.2.0+dfsg-3
  • wolfsslDebian:12all versions · fixed in 4.2.0+dfsg-3

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVSS 3.17.5read 2026-10-23
  • CNACVSS 3.07.5known since 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • NVDweakness (CWE)CWE-787read 2026-10-23
  • FIRST EPSSEPSS score2.0 %2026-11-08
  • OSVaffected packages—
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2019-11-09
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-42mp-7xj4-8whx

Frequently asked questions

What is CVE-2019-18840?

In wolfSSL 4.1.0 through 4.2.0c, there are missing sanity checks of memory accesses in parsing ASN.1 certificate data while handshaking. Specifically, there is a one-byte heap-based buffer overflow inside the DecodedCert structure in GetName in wolfcrypt/src/asn.c because the domain name location index is mishandled. Because a pointer is overwritten, there is an invalid free.

Is CVE-2019-18840 actively exploited?

Active exploitation of CVE-2019-18840 has not been confirmed. Its EPSS score was 2.0% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-18840?

CVE-2019-18840 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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