CVE-2026-9521

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

• ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
• AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.40% probability of exploitation activity in the next 30 days.

EPSS percentile

Ranks above 33.2% of scored records. A rank, not a probability.

NVD base score

2.9 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD analysis status

Deferred. NVD last modified this record on 2026-07-23.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-05-26 02:00Z3 MO AGO

Last updated

2026-05-26 12:21Z3 MO AGO

Reserved

2026-05-25

Assigning CNA

VulDB

Record state

PUBLISHED

Severity

Medium (CVSS 6.3)

CNA CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

Weaknesses

• CWE-20Improper Input ValidationClass
• CWE-1287Improper Validation of Specified Type of InputBase

Data version

5.2

Document digest

657df1a56a13413a2918a59491ab9b717f215d7ee178f0b339fdb7ab6737f0a7

• vuldb.comVDB-365541 | fraillt bitsery std_smart_ptr.h loadFromSharedState improper validation of specified type of inputhttps://vuldb.com/vuln/365541vdb-entrytechnical-description
• vuldb.comVDB-365541 | CTI Indicators (IOB, IOC, IOA)https://vuldb.com/vuln/365541/ctisignaturepermissions-required
• vuldb.comSubmit #814457 | fraillt bitsery 5.2.4 CWE-1287, CWE-843 (Type Confusion)https://vuldb.com/submit/814457third-party-advisory
• gist.github.comhttps://gist.github.com/TrebledJ/750abc64a826f19dd2d6774724629b71exploit
• github.comhttps://github.com/fraillt/bitsery/blob/master/CHANGELOG.md#525-2025-10-09release-notes
• github.comhttps://github.com/fraillt/bitsery/commit/66d16516e24893bebc1c8af52bf2fe9ad0735061patch
• github.comhttps://github.com/fraillt/bitsery/releases/tag/v5.2.5patch
• github.comhttps://github.com/fraillt/bitsery/product