msgpack5: Reserved byte can cause unbounded stream buffering
Collected exploitation and prediction evidence
Risk source coverageCISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.
No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.
cve-program · CVE-2026-107299
Publishedmsgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.
- Source published
- 8 Oct 2026 17:09:47 UTC
- Source modified
- 9 Oct 2026 15:15:00 UTC
- Observed here
- 23 Oct 2026 15:48:27 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
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CVSS 3.1 · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
euvd · EUVD-2026-95110
Publishedmsgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: Oct 8, 2026, 5:09:47 PM
dateUpdated: Oct 9, 2026, 3:15:00 PM
1 related source bulletins · separate from aliases
msrc_CVE-2026-107299: msgpack5: Reserved byte can cause unbounded stream buffering
CVE-2026-107299
- Source published
- Oct 8, 2026, 5:09:47 PM (timezone not stated)
- Source modified
- Oct 9, 2026, 3:15:00 PM (timezone not stated)
- Observed here
- 9 Nov 2026 05:07:36 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.
EUVD CVSS 3.1 · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
nvd · CVE-2026-107299
Publishedmsgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Deferred
Weakness classifications: CWE-228
Original publisher date fields
published: 2026-10-08T17:17:15.850
lastModified: 2026-10-09T16:17:22.147
- Source published
- 8 Oct 2026 17:17:15 UTC
- Source modified
- 9 Oct 2026 16:17:22 UTC
- Observed here
- 25 Oct 2026 04:17:41 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.
CVSS 3.1 · [email protected] · Secondary · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
osv · GHSA-26wq-p25c-j6fv
Published### Impact The reserved MessagePack byte `0xc1` is incorrectly treated as incomplete input. When it appears at the start of a decoder stream, all subsequent data is retained while the decoder waits for bytes that can never make the value valid, allowing memory exhaustion. ### Patches The decoder now rejects `0xc1` as invalid input. Streaming decoders release buffered input and stop after unrecoverable decoding errors. ### Workarounds Reject `0xc1` before streaming input to msgpack5, and enforce stream byte and time limits.
- Source published
- 8 Oct 2026 17:40:01 UTC
- Source modified
- 8 Oct 2026 18:00:08 UTC
- Observed here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.
CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Publisher rating · MODERATE