CVE-2026-9669: bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow
CSIRTS triage
- What
- This vulnerability involves a stack buffer overflow caused by the reuse of bz2.BZ2Decompressor after an error.
- Who is affected
- Deployments using the affected bz2 library.
- Urgency
- Remediation is necessary as it has an unknown severity, but exploitation is not currently reported.
- Action
- Update to the latest version of the bz2 library.
AI-assisted analysis generated from the source advisory — verify against the original.
Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-9669
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-96690.43% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 35% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-9669 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- medium[UPDATE] [medium] CPython: Vulnerability allows Denial of Servicecert-bund
- unknownUSN-8509-1: Python vulnerabilitiesubuntu
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