CVE-2026-48109
No CISA KEV listing is included in this saved record. Exploitation may still have occurred.
FIRST EPSS: 0.51 % · percentile 44.02 % · scored 14 Nov 2026.
Saved 14 Nov 2026 16:37:01 UTC · View this risk record (JSON)
CVE-2026-48109
MessagePack-CSharp · Vulnerability
CVSS 3.1 8.2 HIGHEUVD CVSS 3.1 8.2 CVSS 3.1 · [email protected] · Secondary 8.2 HIGHCVSS_V3 Publisher rating HIGHFixed by MessagePack 2.5.301Fixed by MessagePack 3.1.7KEV status unknown
cve-program · CVE-2026-48109
PublishedMessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
Read the publisher's advisoryeuvd · EUVD-2026-38390
PublishedMessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
Read the publisher's advisorynvd · CVE-2026-48109
PublishedMessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
Read the publisher's advisoryosv · GHSA-hv8m-jj95-wg3x
Published### Impact A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes `Lz4Block` and `Lz4BlockArray`. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an `AccessViolationException` during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This issue affects applications that deserialize untrusted data while LZ4 compression is enabled. ### Patches The v2 versions are patched as of 2.5.301. The v3 versions are patched as of 3.1.7. ### Workarounds Instead of upgrading, an application may take the following precautions: 1. Disable LZ4 compression for untrusted input paths (`Lz4Block`, `Lz4BlockArray`). 2. Only accept compressed payloads from strongly trusted producers. 3. Isolate deserialization in a separate process/container with restart supervision to limit availability impact. ### Resources - MESSAGEPACKCSHARP-010
Read the publisher's advisoryAffected versions, risk and source history
Exploitation and risk
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cve-program · CVE-2026-48109
PublishedMessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
- Source published
- 22 Jun 2026 21:19:54 UTC
- Source modified
- 23 Jun 2026 12:14:29 UTC
- Saved 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
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
euvd · EUVD-2026-38390
PublishedMessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is…
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
Additional publisher context
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: Jun 22, 2026, 9:19:54 PM
dateUpdated: Jun 23, 2026, 12:14:29 PM
- Source published
- Jun 22, 2026, 9:19:54 PM (timezone not stated)
- Source modified
- Jun 23, 2026, 12:14:29 PM (timezone not stated)
- Saved here
- 13 Nov 2026 13:58:42 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
EUVD CVSS 3.1 · 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
nvd · CVE-2026-48109
PublishedMessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is…
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
Additional publisher context
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: Analyzed
Weakness classifications: CWE-20
Original publisher date fields
published: 2026-06-22T22:16:46.617
lastModified: 2026-06-23T17:25:43.420
1 source CPE criteria · context only
- cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*
The original JSON retains the logical configuration operators, exclusions and version bounds.
- Source published
- 22 Jun 2026 22:16:46 UTC
- Source modified
- 23 Jun 2026 17:25:43 UTC
- Saved here
- 25 Oct 2026 12:17:26 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · [email protected] · Secondary · 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
osv · GHSA-hv8m-jj95-wg3x
PublishedMessagePack's LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input
### Impact A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes `Lz4Block` and `Lz4BlockArray`. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an `AccessViolationException` during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This issue affects applications that deserialize untrusted data while LZ4 compression is enabled. ### Patches The v2 versions are patched as of 2.5.301. The v3 versions are patched as of 3.1.7. ### Workarounds Instead of upgrading, an application may take the following precautions: 1. Disable LZ4 compression for untrusted input paths (`Lz4Block`, `Lz4BlockArray`). 2. Only accept compressed payloads from strongly trusted producers. 3. Isolate deserialization in a separate process/container with restart supervision to limit availability impact. ### Resources - MESSAGEPACKCSHARP-010
- Source published
- 11 Jun 2026 20:34:10 UTC
- Source modified
- 10 Sep 2026 03:50:50 UTC
- Saved here
- 23 Oct 2026 16:01:25 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Publisher rating · HIGH