# CVE-2026-18503: Super-linear CPU usage for unbounded input to csv.Sniffer.sniff() > Attackers can cause excessive CPU consumption in applications using Python's csv.Sniffer by providing unbounded input, leading to denial of service. - **Severity:** Low 2.4 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** A user has to click or open something - **Fix available:** Yes - **Published:** 10 Aug 2026 - **Updated:** 14 Oct 2026 - **Also known as:** AZL-95586, AZL-95619, BELL-CVE-2026-18503, BIT-libpython-2026-18503, BIT-python-2026-18503, BIT-python-min-2026-18503, DEBIAN-CVE-2026-18503, ECHO-b98e-b63c-2d5f, GHSA-2345-wr3r-cxf2, MINI-6gv8-j6j8-f588, MINI-98pc-j7vr-cpmx, MINI-cw62-mxgp-hm24, MINI-hv8p-jxrm-8m22, MINI-hxc7-5jqq-h8pg, PSF-2026-35, RHSA-2026:57010, UBUNTU-CVE-2026-18503 ## What is CVE-2026-18503? CVE-2026-18503 is a low-severity denial of service vulnerability in CPython, published on 10 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link. ### Official description Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and consume significant CPU when applications pass unbounded input to csv.Sniffer.sniff(). Weakness: CWE-1176 (Inefficient CPU Computation) ## Which versions are affected by CVE-2026-18503? 3 open source packages ship an affected version, including libpython, python and python-min. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `libpython` | Bitnami | All versions | 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7 | | `python` | Bitnami | All versions | 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7 | | `python-min` | Bitnami | All versions | 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7 | | `python3.10` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | | `python3.10-debug` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | | `python3.10-devel` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | | `python3.10-idle` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | | `python3.10-libs` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | | `python3.10-test` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | | `python3.10-tkinter` | Red Hat:hummingbird:1 | All versions | 0:3.10.21-1.hum1 | ## How do I fix CVE-2026-18503? Upgrade libpython to a fixed version for your release line: 3.10.21, 3.11.16, 3.12.14 or 3.13.15. ## Is CVE-2026-18503 being exploited? There is no known exploitation of CVE-2026-18503 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-18503 and fix it if it is affected. What it is: CVE-2026-18503 is a low-severity denial of service vulnerability in CPython, published on 10 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link. Exploitation: There is no known exploitation of CVE-2026-18503 in the wild and no public exploit code. Affected packages and fixed versions: - libpython (Bitnami): affected all versions; fixed in 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7 - python (Bitnami): affected all versions; fixed in 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7 - python-min (Bitnami): affected all versions; fixed in 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-18503/ (Markdown: https://insights.sbomify.com/CVE-2026-18503/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18503 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18503 - OSV: https://osv.dev/vulnerability/CVE-2026-18503 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-18503/ Summaries are generated and may contain mistakes; the official description above is the record.