# CVE-2020-1967: libssl1.1: Server or client applications that call the SSL_check_chain() function during or after a TLS 1.3 handshake may crash...

CVE-2020-1967 is fixed in 2 products on 1 platform, first by libssl1.1 1.1.1f-1ubuntu2, released April 20, 2020. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2020-1967
- Priority: High
- CVSS: n/a (High)
- EPSS: 0.5334
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 20, 2020

## Description

Server or client applications that call the SSL_check_chain() function during or after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a result of incorrect handling of the "signature_algorithms_cert" TLS extension. The crash occurs if an invalid or unrecognised signature algorithm is received from the peer. This could be exploited by a malicious peer in a Denial of Service attack. OpenSSL version 1.1.1d, 1.1.1e, and 1.1.1f are affected by this issue. This issue did not affect OpenSSL versions prior to 1.1.1d. Fixed in OpenSSL 1.1.1g (Affected 1.1.1d-1.1.1f).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libssl1.1 Ubuntu 20.04 LTS (focal) | 1.1.1f-1ubuntu2 | [libssl1.1 1.1.1f-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libssl1.1-1.1.1f-1ubuntu2.md) | Apr 20, 2020 |
| Linux | openssl Ubuntu 20.04 LTS (focal) | 1.1.1f-1ubuntu2 | [openssl 1.1.1f-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-openssl-1.1.1f-1ubuntu2.md) | Apr 20, 2020 |

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