bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow
Priority LOW 36CWE-121Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Attack requirements
- Present
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 fixed, 1 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-121 and the CVSS impact.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00428 37th percentileScored 2026-11-07
Fix Partial CPython (Python Software Foundation): 3.10.21, 3.11.16, 3.12.14 +3Red Hat: 5 advisoriesRed Hat: 1 fixed, 1 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Python Software Foundation | CPython | before 3.10.21; 3.11.0 to before 3.11.16; 3.12.0 to before 3.12.14; 3.13.0 to before 3.13.14; 3.14.0 to before 3.14.6; 3.15.0a1 to before 3.15.0b3 | 3.10.21, 3.11.16, 3.12.14, 3.13.14, 3.14.6, 3.15.0b3 | Patch available | CNA |
- CPython VendorPython Software Foundation Affected before 3.10.21; 3.11.0 to before 3.11.16; 3.12.0 to before 3.12.14; 3.13.0 to before 3.13.14; 3.14.0 to before 3.14.6; 3.15.0a1 to before 3.15.0b3 Fixed in 3.10.21, 3.11.16, 3.12.14, 3.13.14, 3.14.6, 3.15.0b3 Patch available CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:python:python:*:*:*:*:*:*:*:* | — | — | python-pillow |
- cpe:2.3:a:python:python:*:*:*:*:*:*:*:* Versions — — ·python-pillow
Remediation
- Fix · CNA CPython (Python Software Foundation) Fixed in 3.10.21, 3.11.16, 3.12.14, 3.13.14, 3.14.6, 3.15.0b3
Red Hat 5 advisories
- RHSA-2026:68309 Released 2026-09-16 · Red Hat rating ImportantRed Hat Hardened Images RPMs Security Update
- Red Hat Hardened Images python3.13-3.13.15-1.3.hum1@aarch64, python3.13-3.13.15-1.3.hum1@src, python3.13-3.13.15-1.3.hum1@x86_64 +16
- RHSA-2026:68154 Released 2026-09-16 · Red Hat rating ImportantRed Hat Hardened Images RPMs Security Update
- Red Hat Hardened Images python3.12-3.12.14-1.3.hum1@aarch64, python3.12-3.12.14-1.3.hum1@src, python3.12-3.12.14-1.3.hum1@x86_64 +12
- RHSA-2026:68135 Released 2026-09-16 · Red Hat rating ImportantRed Hat Hardened Images RPMs Security Update
- Red Hat Hardened Images python3.11-3.11.16-1.4.hum1@aarch64, python3.11-3.11.16-1.4.hum1@src, python3.11-3.11.16-1.4.hum1@x86_64 +12
Show 2 more Red Hat advisories
- RHSA-2026:68132 Released 2026-09-16 · Red Hat rating ImportantRed Hat Hardened Images RPMs Security Update
- Red Hat Hardened Images python3.10-3.10.21-1.3.hum1@aarch64, python3.10-3.10.21-1.3.hum1@src, python3.10-3.10.21-1.3.hum1@x86_64 +12
- RHSA-2026:67572 Released 2026-09-15 · Red Hat rating ImportantRed Hat Hardened Images RPMs Security Update
- Red Hat Hardened Images python-unversioned-command-3.14.7-1.2.hum1@noarch@public-hummingbird-aarch64-rpms, python-unversioned-command-3.14.7-1.2.hum1@noarch@public-hummingbird-x86_64-rpms, python3-3.14.7-1.2.hum1@aarch64 +28
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Hardened Images | Fixed | RHSA-2026:67572, RHSA-2026:68132, RHSA-2026:68135, RHSA-2026:68154, RHSA-2026:68309 |
Not affected: 1 product
- Red Hat Hardened Images
Timeline
- 2026-10-02 Threatist record created from CVE-2026-9669
- 2026-10-03 Alias added: GHSA-8jvr-397x-xqh9
References
Patch 8
- https://github.com/python/cpython/pull/150600
- https://github.com/python/cpython/commit/157a5df8cb5d82b33f918a7489e72ce95ceb12b6
- https://github.com/python/cpython/commit/5755d0f083949ff3c5bf3a37e673e24e306b036e
- https://github.com/python/cpython/commit/619a12b2e545391dc436b3af79dda22337382a6f
- https://github.com/python/cpython/commit/d3ca26983dfbccdf609f24ff5877dc3118e4702d
- https://github.com/python/cpython/commit/938ec030e90c5e53f1faac6fab1643f14e4f4a79
- https://github.com/python/cpython/commit/991e6cf86496718c4ef00b362d640e00cb5c85b2
- https://github.com/python/cpython/commit/1ba6135eae75ad8413413caeeedb56ae72320636
Advisory 1
More Python Software Foundation vulnerabilities
- TI-2024-07037 Quadratic complexity parsing cookies with backslashes CVSS 3.1HIGH 7.5
- TI-2024-11791 Bypass extraction filter to modify file metadata outside extraction directory CVSS 3.1MEDIUM 5.3
- TI-2024-00411 Quoted zip-bomb protection for zipfile CVSS 3.1MEDIUM 6.2
- TI-2026-13296 `HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching CVSS 4.0MEDIUM 6.0
- TI-2024-06422 Email header injection due to unquoted newlines CVSS 3.1MEDIUM 5.5
- TI-2026-04606 Possible to hijack modules in current working directory CVSS 4.0MEDIUM 5.6
Sources
- CVE-2026-9669 · CVE Program
- CVE-2026-9669 · NVD
- FIRST EPSS
- GHSA-8jvr-397x-xqh9 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-9669 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences