CVE-2026-9521Public exploitNetwork attack vector

Memory corruption via unchecked shared-pointer aliasing

Published May 26, 2026 · Updated May 26, 2026

Improper type validation in Bitsery 5.2.0 through 5.2.4 allows remote attackers to corrupt application memory via crafted serialized data. The shared-pointer deserialization path reuses a pointer ID and aliases the stored object through reinterpret_cast without confirming type compatibility. An embedding application must deserialize attacker-controlled data with pointer extensions; a mismatch produces invalid memory access or a crash.

CVSS severity7.3
High
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper type validation in Bitsery 5.2.0 through 5.2.4 allows remote attackers to corrupt application memory via crafted serialized data. The shared-pointer deserialization path reuses a pointer ID and aliases the stored object through reinterpret_cast without confirming type compatibility. An embedding application must deserialize attacker-controlled data with pointer extensions; a mismatch produces invalid memory access or a crash.

The record

CVE
CVE-2026-9521
Published
May 26, 2026
Updated
May 26, 2026
Vendor
fraillt
Product
Bitsery
Classifications
CWE-20, CWE-1287
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2026CVE publishedPublication date reported by the CVE source.
  2. May 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.2.0
  2. Affected versionversion=5.2.1
  3. Affected versionversion=5.2.2
  4. Affected versionversion=5.2.3
  5. Affected versionversion=5.2.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

fraillt · Bitseryversion=5.2.0; version=5.2.1; version=5.2.2; version=5.2.3; version=5.2.4

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
7.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-1287Improper Validation of Specified Type of Input

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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