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CVE-2026-107300

msgpack5: Many buffered values can exhaust the streaming decoder stack

7.5 HighFix available

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

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

0.43%Unchanged since Oct 9, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.5

msgpack5: Many buffered values can exhaust the streaming decoder stack

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

Record
CVE-2026-107300
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-674
Updated
2026-11-02
EUVDEUVD-2026-95111 7.5

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

Record
EUVD-2026-95111
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-5x5g-h9x8-2fh9 7.5

msgpack5: Many buffered values can exhaust the streaming decoder stack

Impact

The streaming decoder recursively invokes itself for every complete value remaining in a chunk. A single chunk containing many small valid MessagePack values can exhaust the JavaScript call stack and interrupt the process or stream.

Patches

The streaming decoder now drains concatenated values iteratively with constant call-stack depth.

Workarounds

Limit the number of MessagePack values accepted in one chunk, or split large batches before passing them to the decoder stream.

Record
GHSA-5x5g-h9x8-2fh9
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-674
Updated
2026-11-02
NVD 7.5

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

Record
CVE-2026-107300
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-674
Updated
2026-11-02
OSV 7.5

msgpack5: Many buffered values can exhaust the streaming decoder stack

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

Record
CVE-2026-107300
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-674
Updated
2026-11-02
OSVGHSA-5x5g-h9x8-2fh9 7.5

msgpack5: Many buffered values can exhaust the streaming decoder stack

Impact

The streaming decoder recursively invokes itself for every complete value remaining in a chunk. A single chunk containing many small valid MessagePack values can exhaust the JavaScript call stack and interrupt the process or stream.

Patches

The streaming decoder now drains concatenated values iteratively with constant call-stack depth.

Workarounds

Limit the number of MessagePack values accepted in one chunk, or split large batches before passing them to the decoder stream.

Record
GHSA-5x5g-h9x8-2fh9
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-674
Updated
2026-11-02
OSVAZL-106851 No score

CVE-2026-107300 affecting package msgpack 3.3.0-1

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

Record
AZL-106851
Updated
2026-11-02
OSVCLSA-2026-1791806348 No score

TuxCare security update for msgpack5 (5 CVEs)

TuxCare rebuilt msgpack5 to address 5 CVEs. Fixed in 4.5.1-tuxcare.1.

Record
CLSA-2026-1791806348
Updated
2026-11-02
OSVCLSA-2026-1793302953 No score

TuxCare security update for msgpack5 (7 CVEs)

TuxCare rebuilt msgpack5 to address 7 CVEs. Fixed in 3.6.1-tuxcare.1.

Record
CLSA-2026-1793302953
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
msgpack5
npm
before 6.1.0
6.1.0
msgpack
Azure Linux:3
through 3.3.0-1 None known
msgpack5
TuxCare:npm
From an advisory covering 5 CVEs
4.5.1-tuxcare.0 up to 4.5.1-tuxcare.1, plus listed versions
4.5.1
4.5.1-tuxcare.1
msgpack5
TuxCare:npm
From an advisory covering 7 CVEs
3.6.1-tuxcare.0 up to 3.6.1-tuxcare.1, plus listed versions
3.6.1
3.6.1-tuxcare.1

History

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

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

In short

CVE-2026-107300 is a high vulnerability (CVSS 7.5) in Mcollina Msgpack5, published October 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.43%, the 37th percentile. Fixed in msgpack5 6.1.0.

References

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