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Response snapshot Oct 27, 2026, 06:19 UTC

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VulnerabilityCVE-2026-109869

undici vulnerable to Denial of Service via unhandled error on excessive content-encodings

undici's `fetch()` crashes the Node.js process when a malicious server returns a response with more than five content codings and closes the connection before sending the body.

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.3% in the next 30 days
Sources
3 independent sources

What to do

GitHub lists first patched versions: undici: 6.29.1; undici: 7.30.1; undici: 8.12.2. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-xjj6-f33q-929c (opens a new tab)

What happened

### Impact

undici's `fetch()` crashes the Node.js process when a malicious server returns a response with more than five content codings and closes the connection before sending the body. undici rejects such responses (a content-encoding limit), but it created the internal response stream before that check and returned without attaching an error listener or aborting the request.

The early close then surfaces a content-length mismatch on that orphaned internal stream, which Node.js treats as an unhandled `error` and terminates the process. A remote, unauthenticated server can trigger this with a single response, even when the application correctly catches the `fetch()` rejection. undici 6.x, 7.x, and 8.x are affected.

### Patches

Continue reading

Upgrade to `6.29.1`, `7.30.1`, or `8.12.2`. undici now validates the content-encoding chain before creating the internal body stream and aborts the response when the limit is exceeded, so no error can surface on an orphaned stream.

### Workarounds

None.

Affected package ranges reported by GitHub: undici: >= 6.23.0, < 6.29.1 undici: >= 7.18.0, < 7.30.1 undici: >= 8.0.0, < 8.12.2

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 27.7%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-xjj6-f33q-929c (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xjj6-f33q-929c, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE-2026-109869 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  4. Primary source

    Vendor advisory (via NVD references) (opens a new tab)

    The vendor advisory referenced by the CVE record, for affected versions and fixes.

    Published Date not suppliedChecked

  5. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  6. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-109869, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). undici vulnerable to Denial of Service via unhandled error on excessive content-encodings (CVE-2026-109869). https://kevwire.com/record/CVE-2026-109869

MLA

"undici vulnerable to Denial of Service via unhandled error on excessive content-encodings (CVE-2026-109869)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-109869.

Chicago

KEVWire. "undici vulnerable to Denial of Service via unhandled error on excessive content-encodings (CVE-2026-109869)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-109869.

Evidence summary (plain text)

undici vulnerable to Denial of Service via unhandled error on excessive content-encodings (Oct 23, 2026).
undici's `fetch()` crashes the Node.js process when a malicious server returns a response with more than five content codings and closes the connection before sending the body. undici rejects such responses (a content-encoding limit), but it created the internal response stream before that check and returned without attaching an error listener or aborting the request. The early close then surfaces a content-length mismatch on that orphaned internal stream, which Node.js treats as an unhandled `error` and terminates the process. A remote, unauthenticated server can trigger this with a single response, even when the application correctly catches the `fetch()` rejection. undici 6.x, 7.x, and 8.x are affected.

Upgrade to `6.29.1`, `7.30.1`, or `8.12.2`. undici now validates the content-encoding chain before creating the internal body stream and aborts the response when the limit is exceeded, so no error can surface on an orphaned stream.
CVSS 7.5 (version 3.1; evidence as of Oct 23, 2026; https://github.com/advisories/GHSA-xjj6-f33q-929c).
EPSS 0.3% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-109869&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-xjj6-f33q-929c: https://github.com/advisories/GHSA-xjj6-f33q-929c
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
NVD CVE-2026-109869: https://nvd.nist.gov/vuln/detail/CVE-2026-109869
Vendor advisory (via NVD references): https://cna.openjsf.org/security-advisories.html
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=3500
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-109869&date=2026-10-26
Record ID: CVE-2026-109869.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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