{"answers":{"affected":"It affects 1 product.","exploited":"Yes. Attackers have exploited CVE-2021-26855 in the wild since at least 3 Nov 2021, including in ransomware campaigns.","fix":"No fix has been published for CVE-2021-26855 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 May 2022.","what":"CVE-2021-26855 is a critical server-side request forgery vulnerability in Microsoft Exchange Server, published on 2 Mar 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-2021-26855 and fix it if it is affected.\n\nWhat it is: CVE-2021-26855 is a critical server-side request forgery vulnerability in Microsoft Exchange Server, published on 2 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: Yes. Attackers have exploited CVE-2021-26855 in the wild since at least 3 Nov 2021, including in ransomware campaigns.\n\nAffected product: Microsoft Exchange Server. 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-2021-26855/ (Markdown: https://insights.sbomify.com/CVE-2021-26855/index.md)","id":"CVE-2021-26855","markdown":"https://insights.sbomify.com/CVE-2021-26855/index.md","name":"CVE-2021-26855","record":{"aliases":["GHSA-6784-2mh5-cq56"],"analysis":{"component_type":"server_software","fix_type":"patch","impacts":["code_execution"],"network_reachable":"yes","non_default_config":false,"product_category":"Microsoft Exchange Server","requires_auth":"none","summary":"Attackers can exploit a Server-Side Request Forg flaw in Microsoft Exchange Server to achieve remote code execution.","user_interaction":"not_required","vuln_class":"ssrf"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"microsoft","cpe":[{"product":"exchange_server","vendor":"microsoft"}],"cvss":{"score":9.1,"severity":"critical","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C","version":"3.1"},"cwes":[{"id":"CWE-918","name":"Server-Side Request Forgery"}],"description":"Microsoft Exchange Server Remote Code Execution Vulnerability","ecosystems":[],"exploits":{"exploitdb":4,"first_seen":"2021-03-02","github_poc":53,"max_poc_stars":247,"metasploit":3,"nuclei":1,"refs":[{"date":"2021-03-29T21:10:34Z","kind":"github_poc","ref":"https://github.com/Flangvik/SharpProxyLogon","stars":247,"title":"C# POC for CVE-2021-26855 aka ProxyLogon, supports the classically semi-interactive web shell as well as shellcode injection "},{"date":"2021-04-14T11:12:30Z","kind":"github_poc","ref":"https://github.com/hosch3n/ProxyVulns","stars":176,"title":"[ProxyLogon] CVE-2021-26855 \u0026 CVE-2021-27065 Fixed RawIdentity Bug Exploit. [ProxyOracle] CVE-2021-31195 \u0026 CVE-2021-31196 Exploit Chains. [ProxyShell] CVE-2021-34473 \u0026 CVE-2021-34523 \u0026 CVE-2021-31207 Exploit Chains."},{"date":"2021-03-08T11:54:32Z","kind":"github_poc","ref":"https://github.com/dwisiswant0/proxylogscan","stars":166,"title":"A fast tool to mass scan for a vulnerability on Microsoft Exchange Server that allows an attacker bypassing the authentication and impersonating as the admin (CVE-2021-26855)."},{"date":"2021-03-17T03:56:54Z","kind":"github_poc","ref":"https://github.com/p0wershe11/ProxyLogon","stars":123,"title":"ProxyLogon(CVE-2021-26855+CVE-2021-27065) Exchange Server RCE(SSRF-\u003eGetWebShell)"},{"date":"2021-03-05T08:22:07Z","kind":"github_poc","ref":"https://github.com/cert-lv/exchange_webshell_detection","stars":98,"title":"Detect webshells dropped on Microsoft Exchange servers exploited through \"proxylogon\" group of vulnerabilites (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065)"},{"date":"2021-03-09T16:54:39Z","kind":"github_poc","ref":"https://github.com/h4x0r-dz/CVE-2021-26855","stars":98,"title":null},{"date":"2021-03-11T20:51:48Z","kind":"github_poc","ref":"https://github.com/hackerschoice/CVE-2021-26855","stars":59,"title":"PoC of proxylogon chain SSRF(CVE-2021-26855) to write file by testanull, censored by github"},{"date":"2021-03-10T05:21:19Z","kind":"github_poc","ref":"https://github.com/alt3kx/CVE-2021-26855_PoC","stars":53,"title":null}],"tier":"exploited"},"has_fix":null,"headline":"Microsoft Exchange Server Remote Code Execution","id":"CVE-2021-26855","indexable":true,"kev":{"dateAdded":"2021-11-03","dueDate":"2022-05-03","knownRansomwareCampaignUse":"Known","product":"Exchange Server","requiredAction":"Apply updates per vendor instructions.","vendorProject":"Microsoft","vulnerabilityName":"Microsoft Exchange Server Remote Code Execution Vulnerability"},"kind":"cve","links":{"ecosystem":null,"product":"microsoft:exchange_server","products":["microsoft:exchange_server"],"type":"ssrf","year":"2021"},"n_packages":0,"n_references":1,"next":{"headline":"Microsoft Exchange Server Remote Code Execution","id":"CVE-2021-26857"},"packages":[],"prev":{"headline":"Microsoft Exchange Server Remote Code Execution Vulnerability","id":"CVE-2021-26854"},"products":["Microsoft Exchange Server 2013 Cumulative Update 21","Microsoft Exchange Server 2013 Cumulative Update 22","Microsoft Exchange Server 2013 Cumulative Update 23","Microsoft Exchange Server 2016 Cumulative Update 10","Microsoft Exchange Server 2016 Cumulative Update 11","Microsoft Exchange Server 2016 Cumulative Update 12","Microsoft Exchange Server 2016 Cumulative Update 13","Microsoft Exchange Server 2016 Cumulative Update 14","Microsoft Exchange Server 2016 Cumulative Update 15","Microsoft Exchange Server 2016 Cumulative Update 16","Microsoft Exchange Server 2016 Cumulative Update 17","Microsoft Exchange Server 2016 Cumulative Update 18","Microsoft Exchange Server 2016 Cumulative Update 19","Microsoft Exchange Server 2016 Cumulative Update 8","Microsoft Exchange Server 2016 Cumulative Update 9","Microsoft Exchange Server 2019","Microsoft Exchange Server 2019 Cumulative Update 1","Microsoft Exchange Server 2019 Cumulative Update 2","Microsoft Exchange Server 2019 Cumulative Update 3","Microsoft Exchange Server 2019 Cumulative Update 4","Microsoft Exchange Server 2019 Cumulative Update 5","Microsoft Exchange Server 2019 Cumulative Update 6","Microsoft Exchange Server 2019 Cumulative Update 7","Microsoft Exchange Server 2019 Cumulative Update 8"],"published":"2021-03-02","related":[{"cvss_score":9.8,"headline":"Microsoft Exchange Server Privilege Escalation","id":"CVE-2024-21410","kev_date_added":"2024-02-15","published":"2024-02-13"},{"cvss_score":9.1,"headline":"Microsoft Exchange Server Remote Code Execution","id":"CVE-2021-34473","kev_date_added":"2021-11-03","published":"2021-07-14"},{"cvss_score":9,"headline":"Microsoft Exchange Server Privilege Escalation","id":"CVE-2021-34523","kev_date_added":"2021-11-03","published":"2021-07-14"},{"cvss_score":8.8,"headline":"Microsoft Exchange Server Deserialization of Untrusted Data","id":"CVE-2023-21529","kev_date_added":"2026-04-13","published":"2023-02-14"},{"cvss_score":8.8,"headline":"Microsoft Exchange Server Privilege Escalation","id":"CVE-2022-41080","kev_date_added":"2023-01-10","published":"2022-11-09"},{"cvss_score":8.8,"headline":"Microsoft Exchange Server Server-Side Request Forgery","id":"CVE-2022-41040","kev_date_added":"2022-09-30","published":"2022-10-03"}],"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":"open","licence":"CC0 1.0","name":"CISA KEV"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"},{"class":"open","licence":"CC0","name":"PoC-in-GitHub"}],"ssvc":{"automatable":"yes","exploitation":"active","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-08-19","vendors":["Microsoft"]},"summary":"Attackers can exploit a Server-Side Request Forg flaw in Microsoft Exchange Server to achieve remote code execution.","url":"https://insights.sbomify.com/CVE-2021-26855/"}