{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-34737 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2021-34737 yet. Limit exposure of the affected software until one is available.","what":"CVE-2021-34737 is a medium-severity vulnerability in Cisco Ios Xr, published on 9 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2021-34737 and fix it if it is affected.\n\nWhat it is: CVE-2021-34737 is a medium-severity vulnerability in Cisco Ios Xr, published on 9 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2021-34737 in the wild and no public exploit code.\n\nAffected product: Cisco Ios Xr. No package-level version data is available, so check the vendor advisory linked from the reference page.\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-2021-34737/ (Markdown: https://insights.sbomify.com/CVE-2021-34737/index.md)","id":"CVE-2021-34737","markdown":"https://insights.sbomify.com/CVE-2021-34737/index.md","name":"CVE-2021-34737","record":{"aliases":["GHSA-x6m9-rgr7-fm6p"],"analysis":{"component_type":"operating_system","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Cisco IOS XR","requires_auth":"none","summary":"Remote attackers can crash the DHCPv4 server process via malformed messages, causing temporary service unavailability on Cisco IOS XR devices.","user_interaction":"not_required","vuln_class":"null_dereference"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"cisco","cpe":[{"product":"ios_xr","vendor":"cisco"}],"cvss":{"score":5.8,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","version":"3.1"},"cwes":[{"id":"CWE-476","name":"NULL Pointer Dereference"}],"description":"A vulnerability in the DHCP version 4 (DHCPv4) server feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to trigger a crash of the dhcpd process, resulting in a denial of service (DoS) condition. This vulnerability exists because certain DHCPv4 messages are improperly validated when they are processed by an affected device. An attacker could exploit this vulnerability by sending a malformed DHCPv4 message to an affected device. A successful exploit could allow the attacker to cause a NULL pointer dereference, resulting in a crash of the dhcpd process. While the dhcpd process is restarting, which may take up to approximately two minutes, DHCPv4 server services are unavailable on the affected device. This could temporarily prevent network access to clients that join the network during that time period. Note: Only the dhcpd process crashes and eventually restarts automatically. The router does not reload.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":null,"headline":"Cisco IOS XR Software DHCP Version 4 Server Denial of Service Vulnerability","id":"CVE-2021-34737","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"cisco:ios_xr","products":["cisco:ios_xr"],"type":"null_dereference","year":"2021"},"n_packages":0,"n_references":1,"next":{"headline":"Cisco Identity Services Engine Cross-Site Scripting Vulnerabilities","id":"CVE-2021-34738"},"packages":[],"prev":{"headline":"Cisco Integrated Management Controller GUI Denial of Service Vulnerability","id":"CVE-2021-34736"},"products":["Cisco IOS XR Software"],"published":"2021-09-09","related":[{"cvss_score":8.8,"headline":"Cisco IOS XR Software Discovery Protocol Format String","id":"CVE-2020-3118","kev_date_added":"2021-11-03","published":"2020-02-05"},{"cvss_score":8.6,"headline":"Cisco IOS XR Software DVMRP Memory Exhaustion","id":"CVE-2020-3569","kev_date_added":"2021-11-03","published":"2020-09-23"},{"cvss_score":8.6,"headline":"Cisco IOS XR Software DVMRP Memory Exhaustion","id":"CVE-2020-3566","kev_date_added":"2021-11-03","published":"2020-08-29"},{"cvss_score":7.5,"headline":"Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service","id":"CVE-2010-3035","kev_date_added":"2022-03-25","published":"2010-08-30"},{"cvss_score":6.5,"headline":"Cisco IOS XR Open Port","id":"CVE-2022-20821","kev_date_added":"2022-05-23","published":"2022-05-26"},{"cvss_score":5.9,"headline":"Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service","id":"CVE-2009-2055","kev_date_added":"2022-03-25","published":"2009-08-19"},{"cvss_score":9.8,"headline":"Cisco IOS XR Software Security Hardening Release: September 2026","id":"CVE-2026-20274","kev_date_added":null,"published":"2026-09-02"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2024-11-07","vendors":["Cisco"]},"summary":"Remote attackers can crash the DHCPv4 server process via malformed messages, causing temporary service unavailability on Cisco IOS XR devices.","url":"https://insights.sbomify.com/CVE-2021-34737/"}