Nerdbank.MessagePack: Attacker-controlled stackalloc in DateTime decoding causes…
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-789.
Summary
Nerdbank.MessagePack is a NativeAOT-compatible MessagePack serialization library. Prior to 1.1.62, Nerdbank.MessagePack contains an uncontrolled stack allocation vulnerability in DateTime decoding. A malicious MessagePack payload can declare an oversized timestamp extension length, causing the reader to allocate an attacker-controlled number of bytes on the stack. This can trigger a StackOverflowException, which is not catchable by user code and terminates the process. This vulnerability is fixed in 1.1.62.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| AArnott | Nerdbank.MessagePack | before 1.1.62 | 1.1.62 | Patch available | CNA |
| — | Nerdbank.MessagePack (NuGet) | before 1.1.62 | 1.1.62 | Patch available | GHSA-2cwq-pwfr-wcw3 |
- Nerdbank.MessagePack VendorAArnott Affected before 1.1.62 Fixed in 1.1.62 Patch available CNA
- Nerdbank.MessagePack (NuGet) Vendor— Affected before 1.1.62 Fixed in 1.1.62 Patch available GHSA-2cwq-pwfr-wcw3
Remediation
- Fix · CNA Nerdbank.MessagePack (AArnott) Fixed in 1.1.62
- Fix · GHSA-2cwq-pwfr-wcw3 Nerdbank.MessagePack (NuGet) Fixed in 1.1.62 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-44375
- 2026-10-03 Alias added: GHSA-2cwq-pwfr-wcw3
- 2026-10-25 Priority changed: MEDIUM → LOW
References
Other 6
- https://github.com/AArnott/Nerdbank.MessagePack/security/advisories/GHSA-2cwq-pwfr-wcw3
- https://github.com/AArnott/Nerdbank.MessagePack/pull/941
- https://github.com/AArnott/Nerdbank.MessagePack/commit/7d1eb319cfabe7280e70699946c9a48579fa2f30
- https://github.com/AArnott/Nerdbank.MessagePack/releases/tag/v1.1.62
- https://github.com/AArnott/Nerdbank.MessagePack
- https://github.com/msgpack/msgpack/blob/master/spec.md#timestamp-extension-type
Sources
- CVE-2026-44375 · CVE Program
- CVE-2026-44375 · NVD
- FIRST EPSS
- GHSA-2cwq-pwfr-wcw3 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences