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CVE Record

CVE-2019-1547: ECDSA remote timing attack

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).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2019-1547 is a timing side-channel issue in OpenSSL ECDSA signing. It can matter if an application uses libcrypto with explicit elliptic-curve parameters missing a cofactor. In that narrow case, repeated timing observations may allow private key recovery. OpenSSL states libssl is not vulnerable because it does not use explicit parameters.

Executive priority

Treat this as a targeted cryptographic key-exposure risk, not a broad TLS emergency. Prioritize systems that perform ECDSA signing with OpenSSL libraries, especially older appliances or custom services. Routine OpenSSL patching should close the issue where vendor fixes are available.

Technical view

Affected OpenSSL releases can fall back from side-channel-resistant EC code when an EC group is built from explicit parameters without a cofactor, even if parameters match a named curve. During ECDSA signature operations, an attacker able to time many signatures may recover the key. Fixed versions are 1.1.1d, 1.1.0l, and 1.0.2t.

Likely exposure

Exposure is most likely in custom or embedded software using OpenSSL libcrypto for ECDSA signing with explicit EC parameters. Standard OpenSSL libssl TLS usage is identified as not vulnerable in the CVE description.

Exploitation context

The provided sources do not show KEV listing or active exploitation. Practical exploitation requires timing access to a large number of signatures and the specific explicit-parameter configuration, so exposure is narrower than a general OpenSSL TLS flaw.

Researcher notes

The critical condition is EC group construction using explicit parameters without a cofactor. The sources do not provide affected application names beyond OpenSSL and downstream packages. Validation should focus on code paths and library versions, not only externally visible TLS endpoints.

Mitigation direction

  • Upgrade OpenSSL to 1.1.1d, 1.1.0l, 1.0.2t, or later supported packages.
  • Apply distribution vendor security updates for affected operating systems.
  • Identify applications using OpenSSL libcrypto for ECDSA signing.
  • Avoid explicit EC parameter handling unless vendor guidance confirms it is safe.
  • Check vendor advisories for backported fixes in packaged OpenSSL builds.

Validation and detection

  • Inventory OpenSSL runtime and package versions across servers, containers, appliances, and build images.
  • Confirm whether applications call libcrypto ECDSA signing with explicit EC parameters.
  • Check vendor package changelogs for CVE-2019-1547 backport status.
  • Prioritize review of signing services, authentication systems, tokens, and embedded components.
  • Document any libssl-only exposure separately as lower concern per OpenSSL’s statement.
Prepared
Confidence
high
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
31Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
OpenSSLOpenSSLFixed 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)Listed
Weakness

CWE details

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