CVE-2026-84890

MEDIUMCVSS 5.9/10EPSS 0.25%

Last modified

CVE-2026-84890 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. undici's decompress interceptor decompresses response bodies according to the untrusted Content-Encoding header. While the number of content-encoding layers is capped, the total decompressed output size is unbounded and there is no configuration option to limit it. EPSS estimates a 0.25% chance of exploitation in the next 30 days.

Description

undici's decompress interceptor decompresses response bodies according to the untrusted Content-Encoding header. While the number of content-encoding layers is capped, the total decompressed output size is unbounded and there is no configuration option to limit it. A malicious or faulty upstream can therefore return a small compressed payload, a compression bomb, that expands to hundreds of megabytes or more in client memory, an asymmetric resource consumption that can exhaust memory and crash the process. This affects undici versions from 7.15.0 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.

Metrics

EPSS Probability
0.25%

16.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
NodejsUndici>= 7.15.0, < 7.29.1
NodejsUndici>= 8.0.0, < 8.10.2

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-84890?
undici's decompress interceptor decompresses response bodies according to the untrusted Content-Encoding header. While the number of content-encoding layers is capped, the total decompressed output size is unbounded and there is no configuration option to limit it. A malicious or faulty upstream can therefore return a small compressed payload, a compression bomb, that expands to hundreds of megabytes or more in client memory, an asymmetric resource consumption that can exhaust memory and crash the process. This affects undici versions from 7.15.0 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.
How severe is CVE-2026-84890?
CVE-2026-84890 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 0.25% probability of exploitation in the next 30 days.
How do I fix CVE-2026-84890?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST