Regular Expression Denial of Service in Headers

Answer in brief

CVE-2023-24807 records a High severity (CVSS 7.5) vulnerability in Regular Expression Denial of Service in Headers. The current sources do not mark it as known exploited. The current feed maps undici (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Feb 16, 2023Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Sep 10, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps undici (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
undicinpm	>=0 <5.19.1	5.19.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for undici.
Review the reported fix. Update undici to 5.19.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Feb 16, 2023
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

Upstream source description

### Impact The `Headers.set()` and `Headers.append()` methods are vulnerable to Regular Expression Denial of Service (ReDoS) attacks when untrusted values are passed into the functions. This is due to the inefficient regular expression used to normalize the values in the `headerValueNormalize()` utility function. ### Patches This vulnerability was patched in v5.19.1. ### Workarounds There is no workaround. Please update to an unaffected version. ### References * https://hackerone.com/bugs?report_id=1784449 ### Credits Carter Snook reported this vulnerability.

Quoted source text, attributed separately from HOL analysis.