{"answers":{"affected":"10 open source packages ship an affected version, including org.http4s:http4s-ember-core_2.13, org.http4s:http4s-ember-core_2.12 and org.http4s:http4s-ember-core_3.","exploited":"There is no known exploitation of CVE-2026-54556 in the wild and no public exploit code.","fix":"Upgrade org.http4s:http4s-ember-core_2.13 to a fixed version for your release line: 0.23.35 or 1.0.0-M47.","what":"CVE-2026-54556 is a high-severity denial of service vulnerability in http4s, published on 26 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-2026-54556 and fix it if it is affected.\n\nWhat it is: CVE-2026-54556 is a high-severity denial of service vulnerability in http4s, published on 26 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-2026-54556 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- org.http4s:http4s-ember-core_2.13 (Maven): affected all versions; fixed in 0.23.35\n- org.http4s:http4s-ember-core_2.13 (Maven): affected all versions; fixed in 0.23.35\n- org.http4s:http4s-ember-core_2.13 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47\n- org.http4s:http4s-ember-core_2.13 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47\n- org.http4s:http4s-ember-core_2.12 (Maven): affected all versions; fixed in 0.23.35\n- org.http4s:http4s-ember-core_2.12 (Maven): affected all versions; fixed in 0.23.35\n- org.http4s:http4s-ember-core_3 (Maven): affected all versions; fixed in 0.23.35\n- org.http4s:http4s-ember-core_3 (Maven): affected all versions; fixed in 0.23.35\n- org.http4s:http4s-ember-core_3 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47\n- org.http4s:http4s-ember-core_3 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47\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-2026-54556/ (Markdown: https://insights.sbomify.com/CVE-2026-54556/index.md)","id":"CVE-2026-54556","markdown":"https://insights.sbomify.com/CVE-2026-54556/index.md","name":"CVE-2026-54556","record":{"aliases":["GHSA-vmm3-xgcx-67hm"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":true,"product_category":"Scala HTTP library","requires_auth":"none","summary":"An unauthenticated attacker can cause an out-of-memory denial of service in Http4s Ember backend by exploiting HPACK header expansion flaws.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[],"cvss":{"score":8.2,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-409","name":"Improper Handling of Highly Compressed Data (Data Amplification)"}],"description":"Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/src/main/scala/org/http4s/ember/core/h2/Hpack.scala concatenates HEADERS and CONTINUATION frame fragments and decodes them into a single List, but maxHeaderSize accounting does not include indexed headers or HPACK per-header overhead. A small compressed header block can therefore expand into a much larger decoded representation that remains in memory for processing. Servers exposed to untrusted HTTP/2 traffic and clients directed to an untrusted HTTP/2 server are affected, and concurrent malicious connections can exhaust the process heap. This issue is fixed in versions 0.23.35 and 1.0.0-M47.","ecosystems":["Maven"],"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":"Http4s: HTTP/2 Denial of Service with Ember Backend","id":"CVE-2026-54556","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Maven","product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":10,"n_references":4,"next":{"headline":"mise HTTP backend uses raw version path for install symlink destination","id":"CVE-2026-54557"},"packages":[{"ecosystem":"Maven","fixed":["0.23.35"],"introduced":["0"],"last_affected":[],"package":"org.http4s:http4s-ember-core_2.12","purl":null,"source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["0.23.35"],"introduced":["0"],"last_affected":[],"package":"org.http4s:http4s-ember-core_2.12","purl":"pkg:maven/org.http4s/http4s-ember-core_2.12","source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["0.23.35"],"introduced":["0"],"last_affected":[],"package":"org.http4s:http4s-ember-core_2.13","purl":null,"source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["0.23.35"],"introduced":["0"],"last_affected":[],"package":"org.http4s:http4s-ember-core_2.13","purl":"pkg:maven/org.http4s/http4s-ember-core_2.13","source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["1.0.0-M47"],"introduced":["1.0.0-M1"],"last_affected":[],"package":"org.http4s:http4s-ember-core_2.13","purl":null,"source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["1.0.0-M47"],"introduced":["1.0.0-M1"],"last_affected":[],"package":"org.http4s:http4s-ember-core_2.13","purl":"pkg:maven/org.http4s/http4s-ember-core_2.13","source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["0.23.35"],"introduced":["0"],"last_affected":[],"package":"org.http4s:http4s-ember-core_3","purl":null,"source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["0.23.35"],"introduced":["0"],"last_affected":[],"package":"org.http4s:http4s-ember-core_3","purl":"pkg:maven/org.http4s/http4s-ember-core_3","source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["1.0.0-M47"],"introduced":["1.0.0-M1"],"last_affected":[],"package":"org.http4s:http4s-ember-core_3","purl":null,"source":"GHSA-vmm3-xgcx-67hm"},{"ecosystem":"Maven","fixed":["1.0.0-M47"],"introduced":["1.0.0-M1"],"last_affected":[],"package":"org.http4s:http4s-ember-core_3","purl":"pkg:maven/org.http4s/http4s-ember-core_3","source":"GHSA-vmm3-xgcx-67hm"}],"prev":{"headline":"rtk: Permission-gate bypass in rtk rewrite auto-allow via unsplit shell separators","id":"CVE-2026-54555"},"products":["http4s","http4s-ember-core_2.12","http4s-ember-core_2.13","http4s-ember-core_3"],"published":"2026-08-26","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":"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":"2026-08-29","vendors":["http4s","org.http4s"]},"summary":"An unauthenticated attacker can cause an out-of-memory denial of service in Http4s Ember backend by exploiting HPACK header expansion flaws.","url":"https://insights.sbomify.com/CVE-2026-54556/"}