vulnerability / NVI-00013949 / Revision 2
@logtape/syslog: syslog log injection via unescaped control characters and unvalidated SD-NAME keys
GitHub lists this reviewed advisory for @logtape/syslog, @logtape/syslog, @logtape/syslog. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
8.6 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
0.476%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.41159. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
@logtape/syslog
source listed>= 2.1.0, <= 2.1.4
`@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): ```typescript function escapeStructuredDataValue(value: string): string { return value .replace(/\\/g, "\\\\") .replace(/"/g, '\\"') .replace(/]/g, "\\]"); // \n, \r, and other C0 control characters are not escaped } ``` 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 (`1 …`), 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 va
@logtape/syslog
source listed>= 2.0.0, < 2.0.14
`@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): ```typescript function escapeStructuredDataValue(value: string): string { return value .replace(/\\/g, "\\\\") .replace(/"/g, '\\"') .replace(/]/g, "\\]"); // \n, \r, and other C0 control characters are not escaped } ``` 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 (`1 …`), 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 va
@logtape/syslog
source listed< 1.3.11
`@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): ```typescript function escapeStructuredDataValue(value: string): string { return value .replace(/\\/g, "\\\\") .replace(/"/g, '\\"') .replace(/]/g, "\\]"); // \n, \r, and other C0 control characters are not escaped } ``` 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 (`1 …`), 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 va
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-8h6h-x5pq-56fq ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-54511 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.