# CVE-2026-18149: undici vulnerable to Denial of Service via orphaned RetryHandler response body

CVE-2026-18149 is fixed in 12 products on 1 platform, first by FEDORA-2026-67F78E732B, released September 9, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-18149
- Priority: Routine
- CVSS: 5.9 (Moderate)
- EPSS: 0.0048
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 4, 2026
- Weakness: Missing Release of Resource after Effective Lifetime
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-18149

## Description

undici's retry handler can leave an already-exposed response body pending forever. When a server returns a successful response that declares a Content-Length, sends only part of the body, and closes the connection, the retry handler retries the request. If the retry returns a non-retryable status such as 400, the handler forwards that new response downstream and replaces its internal response stream, but the original response body that the application still holds is never ended or destroyed. As a result calls that read that body never settle, and the configured body timeout does not fire because its timer is tied to the connection parser rather than the orphaned body. An attacker-controlled server can trigger this with two short responses without keeping a connection open, and repeated requests accumulate pending promises and streams that can exhaust application concurrency or memory. This affects undici versions from 7.11.0 up to 7.29.1 and from 8.0.0 up to 8.10.2. Users should upgrade to undici 7.29.1 or 8.10.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | node-undici Debian 14 | 8.10.2+dfsg+~cs3.2.2-1 | [DEBIAN-CVE-2026-18149](https://patchblox.com/security/data/fix/linux/debian-cve-2026-18149.md) | Sep 10, 2026 |
| Linux | nodejs-undici Fedora 43 | 7.29.0-3.fc43 | [FEDORA-2026-67F78E732B](https://patchblox.com/security/data/fix/linux/fedora-2026-67f78e732b.md) | Sep 9, 2026 |
| Linux | nodejs24 amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-debuginfo amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-debugsource amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-devel amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-docs amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-full-i18n amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-libs amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-libs-debuginfo amzn 2023 | 1:24.21.0-1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | nodejs24-npm amzn 2023 | 1:11.19.0-1.24.21.0.1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |
| Linux | v8-13.6-devel amzn 2023 | 3:13.6.233.17-1.24.21.0.1.amzn2023.0.1 | [ALAS2023-2026-3107](https://patchblox.com/security/data/fix/linux/alas2023-2026-3107.md) | Sep 28, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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