{"answers":{"affected":"3 open source packages ship an affected version, including aiosmtplib.","exploited":"There is no known exploitation of CVE-2026-55558 in the wild and no public exploit code.","fix":"Upgrade aiosmtplib to 5.1.2 or later.","what":"CVE-2026-55558 is a medium-severity vulnerability in cole aiosmtplib, 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-2026-55558 and fix it if it is affected.\n\nWhat it is: CVE-2026-55558 is a medium-severity vulnerability in cole aiosmtplib, published on 20 Aug 2026. 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-2026-55558 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- aiosmtplib (PyPI): affected all versions; fixed in 5.1.2\n- aiosmtplib (PyPI): affected all versions; fixed in 5.1.2\n- aiosmtplib (PyPI): affected all versions; fixed in 5.1.2\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-2026-55558/ (Markdown: https://insights.sbomify.com/CVE-2026-55558/index.md)","id":"CVE-2026-55558","markdown":"https://insights.sbomify.com/CVE-2026-55558/index.md","name":"CVE-2026-55558","record":{"aliases":["CLEANSTART-2026-DL97476","CLEANSTART-2026-DR99316","DEBIAN-CVE-2026-55558","ECHO-c2e7-d06a-81e1","GHSA-vxj7-4xrp-5vr4","MINI-46rm-9j23-2r54","MINI-cm8x-4qjv-w54h","PYSEC-2026-3805","UBUNTU-CVE-2026-55558","openSUSE-SU-2026:11569-1"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["data_read","data_modify"],"network_reachable":"yes","non_default_config":false,"product_category":"Python SMTP client","requires_auth":"none","summary":"An active network attacker can inject SMTP responses during STARTTLS negotiation, desynchronizing the protocol state and potentially exposing or modifying data.","user_interaction":"not_required","vuln_class":"other"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[],"cvss":{"score":5.9,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","version":"3.1"},"cwes":[{"id":"CWE-74","name":"Improper Neutralization of Special Elements in Output Used by a Downstream Component"}],"description":"aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.2, SMTPProtocol.start_tls in src/aiosmtplib/protocol.py consumes the server's 220 response and starts the TLS handshake without clearing SMTPProtocol._buffer. An active network attacker can place attacker-chosen SMTP response lines after the plaintext 220 response in the same network segment. The method then calls loop.start_tls; those bytes survive the transport upgrade and are parsed as the first response from inside the TLS session, desynchronizing subsequent SMTP command and response pairs. Connections using start_tls=True or opportunistic STARTTLS are affected, while connections using use_tls=True are not. This issue is fixed in version 5.1.2.","ecosystems":["PyPI","openSUSE:Tumbleweed"],"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":"aiosmtplib: STARTTLS response injection","id":"CVE-2026-55558","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"PyPI","product":null,"products":[],"type":"other","year":"2026"},"n_packages":4,"n_references":3,"next":{"headline":"Yamcs: Remote Code Execution via instance-template argument YAML injection (createInstance)","id":"CVE-2026-55559"},"packages":[{"ecosystem":"PyPI","fixed":["5.1.2"],"introduced":["0"],"last_affected":[],"package":"aiosmtplib","purl":null,"source":"GHSA-vxj7-4xrp-5vr4"},{"ecosystem":"PyPI","fixed":["5.1.2"],"introduced":["0"],"last_affected":[],"package":"aiosmtplib","purl":"pkg:pypi/aiosmtplib","source":"GHSA-vxj7-4xrp-5vr4"},{"ecosystem":"PyPI","fixed":["5.1.2"],"introduced":["0"],"last_affected":[],"package":"aiosmtplib","purl":"pkg:pypi/aiosmtplib","source":"PYSEC-2026-3805"},{"ecosystem":"openSUSE:Tumbleweed","fixed":["5.1.2-1.1"],"introduced":["0"],"last_affected":[],"package":"python-aiosmtplib","purl":"pkg:rpm/opensuse/python-aiosmtplib\u0026distro=openSUSE%20Tumbleweed","source":"openSUSE-SU-2026:11569-1"}],"prev":{"headline":"browse-mcp: Arbitrary file write via unconfined download and state paths","id":"CVE-2026-55557"},"products":["aiosmtplib"],"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":"CC BY 4.0","name":"SUSE","prefix":"openSUSE"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-08-20","vendors":["cole"]},"summary":"An active network attacker can inject SMTP responses during STARTTLS negotiation, desynchronizing the protocol state and potentially exposing or modifying data.","url":"https://insights.sbomify.com/CVE-2026-55558/"}