{"answers":{"affected":"3 open source packages ship an affected version, including nltk.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-72818 exists.","fix":"Upgrade nltk to 3.10.1 or later.","what":"CVE-2026-72818 is a high-severity denial of service vulnerability in nltk, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-72818 and fix it if it is affected.\n\nWhat it is: CVE-2026-72818 is a high-severity denial of service vulnerability in nltk, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-72818 exists.\n\nAffected packages and fixed versions:\n- nltk (PyPI): affected all versions; fixed in 3.10.1\n- nltk (PyPI): affected all versions; fixed in 3.10.1\n- nltk (PyPI): affected all versions; fixed in 3.10.1\n\nTask:\n1. 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.\n2. 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.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-72818/ (Markdown: https://insights.sbomify.com/CVE-2026-72818/index.md)","id":"CVE-2026-72818","markdown":"https://insights.sbomify.com/CVE-2026-72818/index.md","name":"CVE-2026-72818","record":{"aliases":["DEBIAN-CVE-2026-72818","ECHO-798a-87f0-5479","GHSA-qx2g-xrx7-vfh8","MINI-2hcr-878q-x222","PYSEC-2026-3870","UBUNTU-CVE-2026-72818"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Python NLP library","requires_auth":"none","summary":"An attacker can cause a denial of service by submitting specially crafted text that triggers catastrophic backtracking in the NLTK TweetTokenizer URL regex.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"VulnCheck","cpe":[],"cvss":{"score":8.7,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-1333","name":"Inefficient Regular Expression Complexity"}],"description":"The URLS regular expression in nltk/tokenize/casual.py, compiled into TweetTokenizer.WORD_RE and applied by TweetTokenizer.tokenize, contains a naked-domain branch whose domain-label prefix [a-z0-9]+(?:[.\\-][a-z0-9]+)* is unbounded. Input consisting of many alternating label separators can be partitioned in exponentially many ways, and because the branch also requires a trailing top-level domain that such input never supplies, the engine explores those partitions before failing at each offset. A few kilobytes of input therefore consumes seconds to minutes of single-threaded CPU, and the HANG_RE substitution performed before matching does not collapse the pattern. TweetTokenizer is intended for tokenizing untrusted social-media text, so any service that applies it, or the module-level casual_tokenize, to submitted text can be stalled per request without authentication. Version 3.10.1 bounds the label repetition.","ecosystems":["PyPI"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"weaponised"},"has_fix":true,"headline":"NLTK TweetTokenizer URL Pattern Backtracks Catastrophically on Naked-Domain-Like Input","id":"CVE-2026-72818","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"PyPI","product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":3,"n_references":5,"next":{"headline":"Grav CMS before 2.0.13 Remote Code Execution via ZIP Upload","id":"CVE-2026-72819"},"packages":[{"ecosystem":"PyPI","fixed":["3.10.1"],"introduced":["0"],"last_affected":[],"package":"nltk","purl":null,"source":"GHSA-qx2g-xrx7-vfh8"},{"ecosystem":"PyPI","fixed":["3.10.1"],"introduced":["0"],"last_affected":[],"package":"nltk","purl":"pkg:pypi/nltk","source":"GHSA-qx2g-xrx7-vfh8"},{"ecosystem":"PyPI","fixed":["3.10.1"],"introduced":["0"],"last_affected":[],"package":"nltk","purl":"pkg:pypi/nltk","source":"PYSEC-2026-3870"}],"prev":{"headline":"go-chi chi 0.9.0 before 5.3.0 IP Spoofing via X-Forwarded-For","id":"CVE-2026-72817"},"products":["nltk"],"published":"2026-08-20","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"CC BY 4.0","name":"PyPA Advisory Database","prefix":"PYSEC"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"poc","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-09-24","vendors":["nltk"]},"summary":"An attacker can cause a denial of service by submitting specially crafted text that triggers catastrophic backtracking in the NLTK TweetTokenizer URL regex.","url":"https://insights.sbomify.com/CVE-2026-72818/"}