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High, CVSS 8.6

@logtape/syslog: syslog log injection via unescaped control characters and unvalidated SD-NAME keys

CVE-2026-54511GHSA-8h6h-x5pq-56fq

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@logtape/syslog 2.1.5, 2.0.14, 1.3.11), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm @logtape/syslog

    Affected
    >= 2.1.0, <= 2.1.4>= 2.0.0, < 2.0.14< 1.3.11
    Fixed in
    1.3.11, 2.1.5, 2.0.14

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.6 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
EPSS
  • CVE-2026-54511: 0.48% estimated exploitation activity in the next 30 days; percentile 41.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

@logtape/syslog contains two related output-encoding bugs in the structured data formatting code. Both only affect deployments with includeStructuredData: true, which is non-default. 1. Unescaped C0 control characters in structured data values escapeStructuredDataValue() in packages/syslog/src/syslog.ts escapes \, ", and ] per RFC 5424 but does not escape newline (\n), carriage return (\r), or any other C0 control characters (U+0000–U+001F): TCP syslog commonly uses \n as a frame delimiter (RFC 6587, non-transparent framing). If an attacker-controlled value contains a literal newline, that newline terminates the current syslog frame. Bytes following the newline begin a new frame, and if they form a valid RFC 5424 header (<PRI1 …), a downstream collector will accept them as a separate, authentic-looking syslog record. 2. Unvalidated SD-NAME keys Structured data parameter keys are inserted into the message without validation or escaping: RFC 5424 defines SD-NAME as printable US-ASCII…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-8h6h-x5pq-56fq

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-54511

Advisory: @logtape/syslog: syslog log injection via unescaped control characters and unvalidated SD-NAME keys
IDs: CVE-2026-54511, GHSA-8h6h-x5pq-56fq
Record: https://patchnext.com/advisories/cve-2026-54511 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @logtape/syslog 2.1.5, 2.0.14, 1.3.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @logtape/syslog: affected >= 2.1.0, <= 2.1.4; >= 2.0.0, < 2.0.14; < 1.3.11; fixed in 1.3.11, 2.1.5, 2.0.14

## Suggested inspection (read-only)
- `npm ls @logtape/syslog --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @logtape/syslog.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8h6h-x5pq-56fq (GitHub-reviewed advisory GHSA-8h6h-x5pq-56fq lists affected ranges: npm @logtape/syslog >=2.1.0 =2.0.0 =0 <1.3.11)

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