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charset=\"utf-8\"","Content-Transfer-Encoding":"base64","Errors-To":"kernel-team-bounces@lists.ubuntu.com","Sender":"\"kernel-team\" "},"content":"https://ubuntu.com/security/CVE-2026-31431\n\n[ Impact ]\n\nCVE-2026-31431 is a local privilege escalation vulnerability\nin the Linux kernel's AF_ALG (Algorithm) socket subsystem.\n\nThe vulnerability allows an unprivileged local user to perform a deterministic,\ncontrolled 4-byte write into the kernel page cache of any file that the attacker\ncan read, including setuid-root binaries such as /usr/bin/su.\nBecause the page cache is what the kernel consults when executing a file,\nthe corrupted in-memory copy is immediately visible system-wide without the on-disk\nchecksum being altered.\n\n[ Fix ]\n\n* Questing, cherry pick the following patches from upstream:\n - a664bf3d603d crypto: algif_aead - Revert to operating out-of-place\n - 5aa58c3a572b crypto: algif_aead - snapshot IV for async AEAD requests\n - e02494114ebf crypto: authencesn - Do not place hiseq at end of dst for out-of-place decryption\n - 1f48ad3b19a9 crypto: authencesn - Fix src offset when decrypting in-place\n - 31d00156e50e crypto: af_alg - Fix page reassignment overflow in af_alg_pull_tsgl\n\n* Noble, cherry pick the following patches from linux-6.12.y:\n - 41c3aa511e6e crypto: scatterwalk - Backport memcpy_sglist()\n - 183137264401 crypto: algif_aead - use memcpy_sglist() instead of null skcipher\n - 8b88d99341f1 crypto: algif_aead - Revert to operating out-of-place\n - 46fdb39e8322 crypto: algif_aead - snapshot IV for async AEAD requests\n - 7bc058a9b82b crypto: authenc - use memcpy_sglist() instead of null skcipher\n - 89fe118b6470 crypto: authencesn - Do not place hiseq at end of dst for out-of-place decryption\n - 129f12934401 crypto: authencesn - Fix src offset when decrypting in-place\n - c8369a6d62f5 crypto: af_alg - Fix page reassignment overflow in af_alg_pull_tsgl\n\n* Jammy, cherry pick the following patches from linux-5.15.y:\n - 36435a56cd6b crypto: scatterwalk - Backport memcpy_sglist()\n - 17774d99bb43 crypto: algif_aead - use memcpy_sglist() instead of null skcipher\n - 19d43105a97b crypto: algif_aead - Revert to operating out-of-place\n - a920cabdb0b7 crypto: algif_aead - snapshot IV for async AEAD requests\n - e416c41a96c8 crypto: authenc - use memcpy_sglist() instead of null skcipher\n - d589abd8b019 crypto: authencesn - Do not place hiseq at end of dst for out-of-place decryption\n - 723bb1b4a6dd crypto: authencesn - Fix src offset when decrypting in-place\n - 2b781d1d4f93 crypto: af_alg - Fix page reassignment overflow in af_alg_pull_tsgl\n - fd427dd84f22 crypto: algif_aead - Fix minimum RX size check for decryption\n\n[ Test Plan ]\n\nCompiled and boot tested.\nTested using the publicly available exploit.\nTested using LTP crypto testsuite for regressions.\n\n[ Where Problems Could Occur ]\n\nThe fix reverts the 2017 in-place optimization entirely, restoring out-of-place\noperation in algif_aead. A bug in the new out-of-place TX SGL allocation\nor AAD copy path could produce corrupt ciphertext, failed tag verification,\nor memory mismanagement under edge-case input lengths, affecting every consumer\nof the AF_ALG AEAD interface kernel-wide."}