# CVE-2018-0739: libssl1.0.0: Constructed ASN.1 types with a recursive definition (such as can be found in PKCS7) could eventually exceed the stack...

CVE-2018-0739 is fixed in 4 products on 1 platform, first by libssl1.0.0 1.0.2n-1ubuntu5, released March 26, 2018. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2018-0739
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.1860
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 26, 2018

## Description

Constructed ASN.1 types with a recursive definition (such as can be found in PKCS7) could eventually exceed the stack given malicious input with excessive recursion. This could result in a Denial Of Service attack. There are no such structures used within SSL/TLS that come from untrusted sources so this is considered safe. Fixed in OpenSSL 1.1.0h (Affected 1.1.0-1.1.0g). Fixed in OpenSSL 1.0.2o (Affected 1.0.2b-1.0.2n).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libssl1.0.0 Ubuntu 18.04.6 LTS (bionic) | 1.0.2n-1ubuntu5 | [libssl1.0.0 1.0.2n-1ubuntu5](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libssl1.0.0-1.0.2n-1ubuntu5.md) | Mar 26, 2018 |
| Linux | libssl1.1 Ubuntu 18.04.6 LTS (bionic) | 1.1.0g-2ubuntu3 | [libssl1.1 1.1.0g-2ubuntu3](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libssl1.1-1.1.0g-2ubuntu3.md) | Mar 26, 2018 |
| Linux | openssl Ubuntu 18.04.6 LTS (bionic) | 1.1.0g-2ubuntu3 | [openssl 1.1.0g-2ubuntu3](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-openssl-1.1.0g-2ubuntu3.md) | Mar 26, 2018 |
| Linux | openssl1.0 Ubuntu 18.04.6 LTS (bionic) | 1.0.2n-1ubuntu5 | [openssl1.0 1.0.2n-1ubuntu5](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-openssl1.0-1.0.2n-1ubuntu5.md) | Mar 26, 2018 |

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Data as of 2026-11-07T12:40:37Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo