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CVE-2026-8161

multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception

7.5 HighPublic exploitFix available

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.47%Up 0.4 points since May 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.5

multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Record
CVE-2026-8161
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-248, CWE-1321
Updated
2026-11-02
EUVDEUVD-2026-29440 7.5

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Record
EUVD-2026-29440
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-qxch-whhj-8956 7.5

multiparty: Denial of Service via Prototype Pollution leads to Uncaught Exception

Impact

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property (e.g., __proto__, constructor, toString), the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Any service accepting multipart uploads via multiparty is affected.

Patches

Users should upgrade to [email protected] or higher.

Workarounds

None.

Record
GHSA-qxch-whhj-8956
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-248, CWE-1321
Updated
2026-11-02
NVD 7.5

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Record
CVE-2026-8161
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-248, CWE-1321
Updated
2026-11-02
OSV 7.5

multiparty vulnerable to Denial of Service via Prototype Pollution leading to Uncaught Exception

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Record
CVE-2026-8161
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-1321, CWE-248
Updated
2026-11-02
OSVDEBIAN-CVE-2026-8161 7.5

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Record
DEBIAN-CVE-2026-8161
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
Show 4 moreShow less
OSVGHSA-qxch-whhj-8956 7.5

multiparty: Denial of Service via Prototype Pollution leads to Uncaught Exception

Impact

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property (e.g., __proto__, constructor, toString), the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Any service accepting multipart uploads via multiparty is affected.

Patches

Users should upgrade to [email protected] or higher.

Workarounds

None.

Record
GHSA-qxch-whhj-8956
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-1321, CWE-248
Updated
2026-11-02
OSVUBUNTU-CVE-2026-8161 7.5

[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as proto, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.

Record
UBUNTU-CVE-2026-8161
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVCLSA-2026-1784682964 No score

TuxCare security update for multiparty (3 CVEs)

TuxCare rebuilt multiparty to address 3 CVEs. Fixed in 3.3.2-tuxcare.1.

Record
CLSA-2026-1784682964
Updated
2026-11-02
OSVROOT-APP-NPM-CVE-2026-8161 No score

CVE-2026-8161 in @rootio/multiparty - Patched by Root

Root has patched CVE-2026-8161 in the @rootio/multiparty package for Root:npm. Multiple fixed versions available.

Record
ROOT-APP-NPM-CVE-2026-8161
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
multiparty
npm
 through 4.2.3
4.3.0
multiparty
TuxCare:npm
From an advisory covering 3 CVEs
 3.3.2-tuxcare.0 up to 3.3.2-tuxcare.1, plus listed versions
3.3.2
3.3.2-tuxcare.1
node-multiparty
Debian:12
 All versions, plus listed versions
4.2.3-24.2.3-34.2.3-44.2.3-54.3.0+~4.2.1-14.3.0-14.3.1+~4.2.1-1
 None known
node-multiparty
Debian:13
 All versions, plus listed versions
4.2.3-34.2.3-44.2.3-54.3.0+~4.2.1-14.3.0-14.3.1+~4.2.1-1
 None known
node-multiparty
Debian:14
 before 4.3.0-1, plus listed versions
4.2.3-34.2.3-44.2.3-5
4.3.0-1
multiparty
npm
 before 4.3.0
4.3.0
@rootio/multiparty
Root:npm
 before 3.3.2-root.io.1
3.3.2-root.io.1
multiparty
Root:npm
 before 3.3.2-aikido.1
3.3.2-aikido.1
node-multiparty
Ubuntu:16.04:LTS
 All versions, plus listed versions
4.0.0-1
 None known
node-multiparty
Ubuntu:18.04:LTS
 All versions, plus listed versions
4.0.0-14.0.0-1ubuntu1
 None known
Show 6 moreShow less
Affected packages
PackageAffectedFixed
node-multiparty
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.2.1-14.2.1-2
 None known
node-multiparty
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.2.2-24.2.2-3
 None known
node-multiparty
Ubuntu:24.04:LTS
 All versions, plus listed versions
4.2.3-2
 None known
node-multiparty
Ubuntu:25.10
 All versions, plus listed versions
4.2.3-24.2.3-3
 None known
node-multiparty
Ubuntu:26.10
 All versions, plus listed versions
4.2.3-54.3.0+~4.2.1-1
 None known
node-multiparty
Ubuntu:26.04:LTS
 All versions, plus listed versions
4.2.3-34.2.3-4build14.2.3-5
 None known

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
PoC in GitHubSer0n-ath/multiparty-CVE-2026-81612026-05-11

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-8161 is a high vulnerability (CVSS 7.5) in Multiparty, published May 12, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.47%, the 41st percentile. Fixed in multiparty 4.3.0.

References

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