{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-23991 in the wild and no public exploit code.","fix":"Upgrade to a fixed version.","what":"CVE-2021-23991 is a medium-severity denial of service vulnerability in Mozilla Thunderbird, published on 24 Jun 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link."},"fix_prompt":"Check this codebase for CVE-2021-23991 and fix it if it is affected.\n\nWhat it is: CVE-2021-23991 is a medium-severity denial of service vulnerability in Mozilla Thunderbird, published on 24 Jun 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.\nExploitation: There is no known exploitation of CVE-2021-23991 in the wild and no public exploit code.\n\nAffected product: Mozilla Thunderbird. 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-2021-23991/ (Markdown: https://insights.sbomify.com/CVE-2021-23991/index.md)","id":"CVE-2021-23991","markdown":"https://insights.sbomify.com/CVE-2021-23991/index.md","name":"CVE-2021-23991","record":{"aliases":["DEBIAN-CVE-2021-23991","GHSA-x5j6-p8w8-5r65","UBUNTU-CVE-2021-23991"],"analysis":{"component_type":"desktop_application","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Thunderbird email client","requires_auth":"none","summary":"An attacker can prevent encrypted email delivery to a recipient by exploiting invalid subkey handling in Thunderbird's OpenPGP implementation.","user_interaction":"required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"mozilla","cpe":[{"product":"thunderbird","vendor":"mozilla"}],"cvss":{"score":6.8,"severity":"medium","source":"nvd","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","version":"3.1"},"cwes":[],"description":"If a Thunderbird user has previously imported Alice's OpenPGP key, and Alice has extended the validity period of her key, but Alice's updated key has not yet been imported, an attacker may send an email containing a crafted version of Alice's key with an invalid subkey, Thunderbird might subsequently attempt to use the invalid subkey, and will fail to send encrypted email to Alice. This vulnerability affects Thunderbird \u003c 78.9.1.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"Denial of service in Thunderbird","id":"CVE-2021-23991","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"mozilla:thunderbird","products":["mozilla:thunderbird"],"type":"denial_of_service","year":"2021"},"n_packages":0,"n_references":2,"next":{"headline":"Other in Thunderbird","id":"CVE-2021-23992"},"packages":[],"prev":{"headline":"Memory corruption in Firefox","id":"CVE-2021-23988"},"products":["Thunderbird"],"published":"2021-06-24","related":[{"cvss_score":9.8,"headline":"Ambiguous parsing of mail headers","id":"CVE-2026-92238","kev_date_added":null,"published":"2026-09-15"},{"cvss_score":9.8,"headline":"Calendar invitation attachments could launch local executables","id":"CVE-2026-84637","kev_date_added":null,"published":"2026-09-01"},{"cvss_score":9.8,"headline":"Memory corruption in Thunderbird","id":"CVE-2021-43529","kev_date_added":null,"published":"2023-02-16"},{"cvss_score":9.8,"headline":"Memory corruption in Thunderbird","id":"CVE-2019-11703","kev_date_added":null,"published":"2019-07-23"},{"cvss_score":9.8,"headline":"Memory corruption in Thunderbird","id":"CVE-2019-11704","kev_date_added":null,"published":"2019-07-23"},{"cvss_score":9.8,"headline":"Memory corruption in Thunderbird","id":"CVE-2019-11705","kev_date_added":null,"published":"2019-07-23"},{"cvss_score":9.8,"headline":"Use after free in Thunderbird","id":"CVE-2018-18512","kev_date_added":null,"published":"2019-04-26"}],"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":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2024-08-03","vendors":["Mozilla"]},"summary":"An attacker can prevent encrypted email delivery to a recipient by exploiting invalid subkey handling in Thunderbird's OpenPGP implementation.","url":"https://insights.sbomify.com/CVE-2021-23991/"}