Vulnerability · Published Jun 8, 2026 · Assigned by PSF
CVE-2026-9669bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow
High 8.2
In plain English
A high-severity stack buffer overflow in CPython from Python Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
bz2.BZ2Decompressor objects could be reused after a decompression error. If an application caught the resulting OSError and retried with the same decompressor, crafted input could cause the decompressor to resume from an invalid internal state and perform out-of-bounds writes to a stack buffer. This could crash the process when processing untrusted data.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.24 | python3 | 3.14.7-r0 | ALPINE-CVE-2026-9669 |
| Debian:12 | python3.11 | 3.11.2-6+deb12u9 | DEBIAN-CVE-2026-9669 |
| Debian:13 | python3.13 | 3.13.5-2+deb13u3 | DEBIAN-CVE-2026-9669 |
| Debian:14 | python3.14 | 3.14.6-1 | DEBIAN-CVE-2026-9669 |
| Ubuntu:22.04:LTS | python3.10 | 3.10.12-1~22.04.16 | UBUNTU-CVE-2026-9669 |
| Ubuntu:22.04:LTS | python3.10 | 3.10.12-1~22.04.16 | USN-8509-1 |
| Ubuntu:24.04:LTS | python3.12 | 3.12.3-1ubuntu0.15 | USN-8509-1 |
| Ubuntu:24.04:LTS | python3.12 | 3.12.3-1ubuntu0.15 | UBUNTU-CVE-2026-9669 |
| Ubuntu:25.10 | python3.13 | no fix listed | UBUNTU-CVE-2026-9669 |
| Ubuntu:25.10 | python3.14 | no fix listed | UBUNTU-CVE-2026-9669 |
| Ubuntu:26.04:LTS | python3.14 | 3.14.4-1ubuntu0.1 | USN-8509-1 |
| Ubuntu:26.04:LTS | python3.14 | 3.14.4-1ubuntu0.1 | UBUNTU-CVE-2026-9669 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Python Software Foundation | CPython | 0 – before 3.10.213.11.0 – before 3.11.163.12.0 – before 3.12.143.13.0 – before 3.13.143.14.0 – before 3.14.63.15.0a1 – before 3.15.0b3 |
Weakness: CWE-121 · Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References
- https://github.com/python/cpython/pull/150600 patch
- https://mail.python.org/archives/list/security-announce@python.org/thread/DBJZETMGUIFK7DVUWMOXHD3Z6IX2QPSX/ vendor-advisory
- https://github.com/python/cpython/issues/150599 issue-tracking
- https://github.com/python/cpython/commit/157a5df8cb5d82b33f918a7489e72ce95ceb12b6 patch
- https://github.com/python/cpython/commit/5755d0f083949ff3c5bf3a37e673e24e306b036e patch
- https://github.com/python/cpython/commit/619a12b2e545391dc436b3af79dda22337382a6f patch
- https://github.com/python/cpython/commit/d3ca26983dfbccdf609f24ff5877dc3118e4702d patch
- https://github.com/python/cpython/commit/938ec030e90c5e53f1faac6fab1643f14e4f4a79 patch
- https://github.com/python/cpython/commit/991e6cf86496718c4ef00b362d640e00cb5c85b2 patch
- https://github.com/python/cpython/commit/1ba6135eae75ad8413413caeeedb56ae72320636 patch
- http://www.openwall.com/lists/oss-security/2026/06/08/17