{"answers":{"affected":"1 open source package ship an affected version, including cosmian_kyber.","exploited":"There is no known exploitation of RUSTSEC-2026-0288 in the wild and no public exploit code.","fix":"No fix has been published for RUSTSEC-2026-0288 yet. Limit exposure of the affected software until one is available.","what":"RUSTSEC-2026-0288 is a vulnerability in cosmian_kyber, published on 16 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 RUSTSEC-2026-0288 and fix it if it is affected.\n\nWhat it is: RUSTSEC-2026-0288 is a vulnerability in cosmian_kyber, published on 16 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 RUSTSEC-2026-0288 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- cosmian_kyber (crates.io): affected from 0.0.0-0; no fix listed\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/RUSTSEC-2026-0288/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0288/index.md)","id":"RUSTSEC-2026-0288","markdown":"https://insights.sbomify.com/RUSTSEC-2026-0288/index.md","name":"RUSTSEC-2026-0288","record":{"aliases":[],"analysis":{"component_type":"library","fix_type":"configuration_change","impacts":["data_read","security_bypass"],"network_reachable":"yes","non_default_config":true,"product_category":"Rust Kyber library","requires_auth":"none","summary":"Enabling the AVX2 feature in cosmian_kyber breaks implicit rejection, allowing attackers to recover static secret keys via chosen-ciphertext attacks.","user_interaction":"not_required","vuln_class":"weak_cryptography"},"analysis_generated_by":"qwen3.8-flash-next","assigner":null,"cpe":[],"cvss":{"score":null,"severity":null,"source":null,"vector":null,"version":null},"cwes":[],"description":"## Summary\n\n`cosmian_kyber` is a fork of `Argyle-Software/kyber` and inherits a broken\nconstant-time conditional-move routine `cmov` in its AVX2 backend. When built\nwith the opt-in `avx2` feature on x86_64, `cmov` is a no-op: it never performs\nthe copy. That `cmov` is the step that applies the Fujisaki-Okamoto (FO) implicit\nrejection during decapsulation. With it disabled, decapsulating an *invalid*\nciphertext no longer returns a key-independent pseudorandom value; it returns a\nvalue that depends on the decrypted plaintext of the attacker-chosen ciphertext.\nThis restores the chosen-ciphertext decryption oracle that the FO transform\nexists to remove, and yields full recovery of the static secret key.\n\nThe attack requires no timing measurement, no side channel, and no faults; only\nthe ability to submit ciphertexts to a decapsulation operation under a reused\nkey pair and observe the resulting shared secret. See the linked pull request\nfor the root cause and the reachable call path.\n\n## Affected configuration\n\nReachable only in builds with `features = [\"avx2\"]` on an x86_64 target. The\ndefault (reference) backend and all non-x86_64 targets are unaffected.\n\n## Impact\n\nComplete IND-CCA break. The plaintext-checking oracle drives a standard\nchosen-ciphertext key-recovery attack and extracts the entire static secret key.\nAny protocol reusing a Kyber key pair across decapsulations is exposed;\nephemeral-only key shares are not. The identical defect in the parent crate was\nverified end to end on ML-KEM-768 (full key recovered in 4,272 decapsulation\nqueries).\n\n## Maintenance status\n\n`cosmian_kyber` is a stale fork (last published 0.1.0, January 2023) of an\nunmaintained upstream, and no fixed release is expected.\n\n## Mitigation\n\n- If remaining on this crate, do not enable the `avx2` feature; the default\n  reference backend performs implicit rejection correctly.\n- Do not reuse a Kyber key pair across decapsulations.\n\n## Credit\n\nReported by 007bsd.","ecosystems":["crates.io"],"exploits":{"exploitdb":null,"first_seen":null,"github_poc":null,"max_poc_stars":null,"metasploit":null,"nuclei":null,"refs":[],"tier":null},"has_fix":false,"headline":"cosmian_kyber: AVX2 backend skips Fujisaki-Okamoto implicit rejection, enabling chosen-ciphertext key recovery","id":"RUSTSEC-2026-0288","indexable":true,"kev":null,"kind":"advisory","links":{"ecosystem":"crates.io","product":null,"products":[],"type":"weak_cryptography","year":"2026"},"n_packages":1,"n_references":null,"packages":[{"ecosystem":"crates.io","fixed":[],"introduced":["0.0.0-0"],"last_affected":[],"package":"cosmian_kyber","purl":"pkg:cargo/cosmian_kyber","source":"RUSTSEC-2026-0288"}],"products":null,"published":"2026-08-16","related":[],"sources":[{"class":"open","licence":"CC0 1.0","name":"RustSec","prefix":"RUSTSEC"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":null,"updated":null,"vendors":null},"summary":"Enabling the AVX2 feature in cosmian_kyber breaks implicit rejection, allowing attackers to recover static secret keys via chosen-ciphertext attacks.","url":"https://insights.sbomify.com/RUSTSEC-2026-0288/"}