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🛡️ CVE-2026-2581 — undici

🟡 CVSS 5.9 — Medium ✅ No Known Exploit CWE-770 OSV
5.9
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Undici has Unbounded Memory Consumption in its DeduplicationHandler via Response Buffering that leads to DoS

Impact

This is an uncontrolled resource consumption vulnerability (CWE-400) that can lead to Denial of Service (DoS).

In vulnerable Undici versions, when interceptors.deduplicate() is enabled, response data for deduplicated requests could be accumulated in memory for downstream handlers. An attacker-controlled or untrusted upstream endpoint can exploit this with large/chunked responses and concurrent identical requests, causing high memory usage and potential OOM process termination.

Impacted users are applications that use Undici’s deduplication interceptor against endpoints that may produce large or long-lived response bodies.

Patches

The issue has been patched by changing deduplication behavior to stream response chunks to downstream handlers as they arrive (instead of full-body accumulation), and by preventing late deduplication when body streaming has already started.

Users should upgrade to the first official Undici (and Node.js, where applicable) releases that include this patch.

Workarounds

If upgrading immediately is not possible:

  • Disable interceptors.deduplicate() for affected clients/routes.
  • Use skipHeaderNames with a marker header to force high-risk requests to bypass deduplication.
  • Avoid concurrent identical requests to untrusted endpoints that may return very large/chunked bodies.
  • Apply upstream/proxy response-size and timeout limits.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-2581 is classified as CWE-770: Allocation of Resources Without Limits. Resources are allocated on request with no cap, so a client can exhaust them.

Affected software

CVE-2026-2581 is recorded against 1 package.

  • undici

Timeline and source

Published on 13 March 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
hackerone.com (Web)
cna.openjsf.org (Web)
github.com (Package)

Other advisories for this package

undici has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-770: Allocation of Resources Without Limits) in other software:

CVE-2026-2581 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity MEDIUM
CVSS Score 5.9
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-770
Public Exploit ✅ No
Source OSV
Published 2026-03-13
Updated 2026-08-20
Modified 2026-06-17
Fix URL N/A

Affected Packages

Software From version Fixed in
undici — —

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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