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High, CVSS 8.7amended

Pretext: Algorithmic Complexity (DoS) in the text analysis phase

GHSA-5478-66c3-rhxr

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@chenglou/pretext 0.0.5), 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

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

isRepeatedSingleCharRun() in src/analysis.ts (line 285) re-scans the entire accumulated segment on every merge iteration during text analysis, producing O(n²) total work for input consisting of repeated identical punctuation characters. An attacker who controls text passed to prepare() can block the main thread for ~20 seconds with 80KB of input (e.g., "(".repeat(80000)). Tested against commit 9364741d3562fcc65aacc50953e867a5cb9fdb23 (v0.0.4) on Node.js v24.12.0, Windows x64. A standalone PoC and detailed write-up are attached below. --- Root Cause The buildMergedSegmentation() function (line 795) processes text segments produced by Intl.Segmenter. When consecutive non-word-like segments consist of the same single character (e.g., (, , !, #), the code merges them into one growing segment (line 859): Before each merge, it calls isRepeatedSingleCharRun() (line 857) to verify that ALL characters in the accumulated segment match the new character: Intl.Segmenter with granularity: 'word'…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-5478-66c3-rhxr

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-5478-66c3-rhxr

Agent brief

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# Patch Next advisory brief: GHSA-5478-66c3-rhxr

Advisory: Pretext: Algorithmic Complexity (DoS) in the text analysis phase
IDs: GHSA-5478-66c3-rhxr
Record: https://patchnext.com/advisories/ghsa-5478-66c3-rhxr (revision 3, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @chenglou/pretext 0.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @chenglou/pretext: affected <= 0.0.4; fixed in 0.0.5

## Suggested inspection (read-only)
- `npm ls @chenglou/pretext --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 @chenglou/pretext.
- 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://osv.dev/vulnerability/GHSA-5478-66c3-rhxr (OSV record GHSA-5478-66c3-rhxr lists affected ranges: npm @chenglou/pretext >=0 <0.0.5 (fixed))
- Verified: https://github.com/advisories/GHSA-5478-66c3-rhxr (GitHub-reviewed advisory GHSA-5478-66c3-rhxr lists affected ranges: npm @chenglou/pretext >=0 <=0.0.4)

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