CVE-2026-23886Network attack vector

Remote process crash via invalid traceparent hex

Published Jan 19, 2026 · Updated Jan 19, 2026

Improper input validation in Swift W3C TraceContext before 1.0.0-beta.5 allows remote attackers to crash a process via a traceparent header. The TraceContext initializer passes trace IDs, span IDs, and flags to Hex.convert, whose default branches call preconditionFailure for uppercase or other invalid hex bytes instead of throwing a decoding error. Network reachability requires an application to parse incoming trace headers, commonly through Swift OTel before 1.0.4, and a malformed hex byte terminates that process.

CVSS severity5.3
Medium
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Swift W3C TraceContext before 1.0.0-beta.5 allows remote attackers to crash a process via a traceparent header. The TraceContext initializer passes trace IDs, span IDs, and flags to Hex.convert, whose default branches call preconditionFailure for uppercase or other invalid hex bytes instead of throwing a decoding error. Network reachability requires an application to parse incoming trace headers, commonly through Swift OTel before 1.0.4, and a malformed hex byte terminates that process.

The record

CVE
CVE-2026-23886
Published
Jan 19, 2026
Updated
Jan 19, 2026
Vendor
Swift OTel
Product
Swift W3C TraceContext
Classifications
CWE-20, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=swift-otel < 1.0.4
  2. Affected versionversion=swift-w3c-trace-context < 1.0.0-beta.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Swift OTel · Swift W3C TraceContextversion=swift-otel < 1.0.4; version=swift-w3c-trace-context < 1.0.0-beta.5

Published CVSS scores

5.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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