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High, CVSS 8.7amended

node-tar: Negative tar entry size causes infinite loop in archive replace

CVE-2026-59874GHSA-8x88-c5mf-7j5w

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (tar 7.5.18), 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 tar

    Affected
    <= 7.5.17
    Fixed in
    7.5.18

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
  • CVE-2026-59874: 0.43% estimated exploitation activity in the next 30 days; percentile 37.72 (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.

Summary A checksum-valid tar archive with a negative base-256 encoded entry size can make tar.replace() loop forever while scanning the existing archive. Applications that update attacker-controlled tar archives can have a worker process pinned indefinitely, causing denial of service. Details The public tar.replace() API scans the existing archive before appending replacement entries. During this scan, it parses each tar header and advances the archive position by the parsed entry size rounded to a 512-byte block boundary. Tar supports base-256 encoded numeric fields. A crafted header can encode the entry size as -512 while still carrying a valid checksum. The replace scan accepts that parsed negative size and uses it in the position-advance calculation. For a size of -512, the computed body skip is -512. The scan then adds the normal 512-byte header step, resulting in no net progress. The scanner repeatedly parses the same header forever and never reaches the append step. This is…

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

    Amended from ghsa record GHSA-8x88-c5mf-7j5w

  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-8x88-c5mf-7j5w

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-2026-59874

Advisory: node-tar: Negative tar entry size causes infinite loop in archive replace
IDs: CVE-2026-59874, GHSA-8x88-c5mf-7j5w
Record: https://patchnext.com/advisories/cve-2026-59874 (revision 3, source checked 26 Oct 2026, 12:57 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: tar 7.5.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm tar: affected <= 7.5.17; fixed in 7.5.18

## Suggested inspection (read-only)
- `npm ls tar --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 tar.
- 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-8x88-c5mf-7j5w (OSV record GHSA-8x88-c5mf-7j5w lists affected ranges: npm tar >=0 <7.5.18 (fixed))
- Verified: https://github.com/advisories/GHSA-8x88-c5mf-7j5w (GitHub-reviewed advisory GHSA-8x88-c5mf-7j5w lists affected ranges: npm tar >=0 <=7.5.17)

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