# CVE-2019-18840: libwolfssl23: In wolfSSL 4.1.0 through 4.2.0c, there are missing sanity checks of memory accesses in parsing ASN.1 certificate data...

CVE-2019-18840 is fixed in libwolfssl23 on 1 platform by libwolfssl23 4.2.0+dfsg-3 (version 4.2.0+dfsg-3), released November 9, 2019. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2019-18840
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0197
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Nov 9, 2019

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libwolfssl23 Ubuntu 20.04 LTS (focal) | 4.2.0+dfsg-3 | [libwolfssl23 4.2.0+dfsg-3](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libwolfssl23-4.2.0-dfsg-3.md) | Nov 9, 2019 |

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