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compression vulnerable to Denial of Service via memory leak on premature response close

High severity GitHub Reviewed Published Sep 11, 2026 in expressjs/compression • Updated Oct 5, 2026

Package

npm compression (npm)

Affected versions

< 1.8.2

Patched versions

1.8.2

Description

Impact

A vulnerability in compression < 1.8.2 allows an attacker to trigger a Denial of Service (DoS) by disconnecting while a compressed response is being sent. When the client aborts the connection before the response finishes, the zlib stream created to compress that response is never destroyed, so each aborted compressed response leaks its native zlib memory. Repeated aborted requests can exhaust available memory. All applications using compression are affected.

Patches

Users should upgrade to 1.8.2.

Workarounds

None.

References

@UlisesGascon UlisesGascon published to expressjs/compression Sep 11, 2026
Published by the National Vulnerability Database Sep 11, 2026
Published to the GitHub Advisory Database Oct 5, 2026
Reviewed Oct 5, 2026
Last updated Oct 5, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(47th percentile)

Weaknesses

Missing Release of Memory after Effective Lifetime

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse. Learn more on MITRE.

Incomplete Cleanup

The product does not properly clean up and remove temporary or supporting resources after they have been used. Learn more on MITRE.

CVE ID

CVE-2026-87776

GHSA ID

GHSA-vc2v-76pw-4v95

Source code

Credits

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