CVE-2026-107297
msgpack5: Quadratic parsing in the streaming decoder
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
5.9
msgpack5: Quadratic parsing in the streaming decoder
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
- Record
CVE-2026-107297- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
EUVDEUVD-2026-95108
5.9
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
- Record
EUVD-2026-95108- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-gcx5-hxj7-gpqq
5.9
msgpack5: Quadratic parsing in the streaming decoder
Impact
The streaming decoder reparses an incomplete container from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack value across many small chunks, causing quadratic CPU usage and blocking the event loop.
Patches
The decoder now preserves incremental container state so completed elements are not parsed again when more input arrives.
Workarounds
Buffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value.
- Record
GHSA-gcx5-hxj7-gpqq- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
NVD
5.9
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
- Record
CVE-2026-107297- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
OSV
5.9
msgpack5: Quadratic parsing in the streaming decoder
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
- Record
CVE-2026-107297- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
OSVGHSA-gcx5-hxj7-gpqq
5.9
msgpack5: Quadratic parsing in the streaming decoder
Impact
The streaming decoder reparses an incomplete container from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack value across many small chunks, causing quadratic CPU usage and blocking the event loop.
Patches
The decoder now preserves incremental container state so completed elements are not parsed again when more input arrives.
Workarounds
Buffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value.
- Record
GHSA-gcx5-hxj7-gpqq- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
OSVAZL-106842 No score
CVE-2026-107297 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 reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
- Record
AZL-106842- 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
| Package | Affected | Fixed |
|---|---|---|
msgpack5npm |
before 6.1.0 | 6.1.0 |
msgpackAzure Linux:3 |
through 3.3.0-1 | None known |
msgpack5TuxCare: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 |
msgpack5TuxCare: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
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-107297 is a medium vulnerability (CVSS 5.9) 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 0.39%, the 33rd percentile. Fixed in msgpack5 6.1.0.
References
github.com/mcollina/msgpack5/security/advisories/GHSA-gcx5-hxj7-gpqq
github.com/mcollina/msgpack5/commit/e4827641d3105e295cbbd56e9c5389978547eab4
github.com/mcollina/msgpack5/releases/tag/v6.1.0
github.com/advisories/GHSA-gcx5-hxj7-gpqq
nvd.nist.gov/vuln/detail/CVE-2026-107297
github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107297.json
github.com/mcollina/msgpack5