{"id":"CVE-2025-40063","state":"PUBLISHED","title":"crypto: comp - Use same definition of context alloc and free ops","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: comp - Use same definition of context alloc and free ops\n\nIn commit 42d9f6c77479 (\"crypto: acomp - Move scomp stream allocation\ncode into acomp\"), the crypto_acomp_streams struct was made to rely on\nhaving the alloc_ctx and free_ctx operations defined in the same order\nas the scomp_alg struct. But in that same commit, the alloc_ctx and\nfree_ctx members of scomp_alg may be randomized by structure layout\nrandomization, since they are contained in a pure ops structure\n(containing only function pointers). If the pointers within scomp_alg\nare randomized, but those in crypto_acomp_streams are not, then\nthe order may no longer match. This fixes the problem by removing the\nunion from scomp_alg so that both crypto_acomp_streams and scomp_alg\nwill share the same definition of alloc_ctx and free_ctx, ensuring\nthey will always have the same layout.","publishedAt":"2025-10-28T11:48:34.549Z","updatedAt":"2026-08-05T12:07:28.106Z","severity":{"score":7,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42d9f6c774790d290c175e8775ce9f1366438098","status":"affected","lessThan":"779d3b6f2d32c5f1da6163e959abe1e1ffe2945b","versionType":"git"},{"version":"42d9f6c774790d290c175e8775ce9f1366438098","status":"affected","lessThan":"f75f66683ded09f7135aef2e763c245a07c8271a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["crypto/842.c","crypto/lz4.c","crypto/lz4hc.c","crypto/lzo-rle.c","crypto/lzo.c","drivers/crypto/nx/nx-common-powernv.c","drivers/crypto/nx/nx-common-pseries.c","include/crypto/internal/scompress.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.17.3","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["crypto/842.c","crypto/lz4.c","crypto/lz4hc.c","crypto/lzo-rle.c","crypto/lzo.c","drivers/crypto/nx/nx-common-powernv.c","drivers/crypto/nx/nx-common-pseries.c","include/crypto/internal/scompress.h"]}],"references":["https://git.kernel.org/stable/c/779d3b6f2d32c5f1da6163e959abe1e1ffe2945b","https://git.kernel.org/stable/c/f75f66683ded09f7135aef2e763c245a07c8271a"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/40xxx/CVE-2025-40063.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40063","state":"PUBLISHED","datePublished":"2025-10-28T11:48:34.549Z","dateUpdated":"2026-08-05T12:07:28.106Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.159Z"},"containers":{"cna":{"title":"crypto: comp - Use same definition of context alloc and free ops","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: comp - Use same definition of context alloc and free ops\n\nIn commit 42d9f6c77479 (\"crypto: acomp - Move scomp stream allocation\ncode into acomp\"), the crypto_acomp_streams struct was made to rely on\nhaving the alloc_ctx and free_ctx operations defined in the same order\nas the scomp_alg struct. But in that same commit, the alloc_ctx and\nfree_ctx members of scomp_alg may be randomized by structure layout\nrandomization, since they are contained in a pure ops structure\n(containing only function pointers). If the pointers within scomp_alg\nare randomized, but those in crypto_acomp_streams are not, then\nthe order may no longer match. This fixes the problem by removing the\nunion from scomp_alg so that both crypto_acomp_streams and scomp_alg\nwill share the same definition of alloc_ctx and free_ctx, ensuring\nthey will always have the same layout."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42d9f6c774790d290c175e8775ce9f1366438098","status":"affected","lessThan":"779d3b6f2d32c5f1da6163e959abe1e1ffe2945b","versionType":"git"},{"version":"42d9f6c774790d290c175e8775ce9f1366438098","status":"affected","lessThan":"f75f66683ded09f7135aef2e763c245a07c8271a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["crypto/842.c","crypto/lz4.c","crypto/lz4hc.c","crypto/lzo-rle.c","crypto/lzo.c","drivers/crypto/nx/nx-common-powernv.c","drivers/crypto/nx/nx-common-pseries.c","include/crypto/internal/scompress.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.17.3","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["crypto/842.c","crypto/lz4.c","crypto/lz4hc.c","crypto/lzo-rle.c","crypto/lzo.c","drivers/crypto/nx/nx-common-powernv.c","drivers/crypto/nx/nx-common-pseries.c","include/crypto/internal/scompress.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/779d3b6f2d32c5f1da6163e959abe1e1ffe2945b"},{"url":"https://git.kernel.org/stable/c/f75f66683ded09f7135aef2e763c245a07c8271a"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The affected algorithms (lzo, lzo-rle, lz4, lz4hc, 842, nx842) are reached only through local kernel consumers — zswap page compression, UBIFS, and boot-time crypto self-tests — via `crypto_scomp_init_tfm()`. The only remote consumer of the compression API, IPComp/xfrm, uses deflate, which is an `acomp_alg` with its own `crypto_acomp_streams` and is unaffected.\nAC:H - Manifestation requires a kernel built with CONFIG_RANDSTRUCT_FULL/PERFORMANCE (the default is RANDSTRUCT_NONE) *and* a per-build randomization seed that actually transposes `alloc_ctx`/`free_ctx` in the pure-ops anonymous struct. Both are fixed at compile time and entirely beyond the attacker's control, so a susceptible target must be found rather than created.\nPR:L - On a susceptible build, an unprivileged local process can drive the faulty path simply by generating memory pressure that makes zswap compress its pages, which triggers per-CPU `alloc_ctx()` calls in `acomp_stream_workfn()`; no capability or namespace privilege is needed. Only basic local code execution is required.\nUI:N - Compression is performed by the kernel as part of normal swap/filesystem operation driven by the attacker's own allocations. No victim action such as mounting a filesystem or opening a file is required.\nS:U - The corruption is confined to kernel memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed. This is a standard in-kernel memory-corruption issue.\nC:H - The garbage return value of the mis-called `free_ctx` becomes `stream->ctx` and is used as the compression workspace, and the uncontrolled `kvfree()` corrupts the heap, yielding primitives that can be leveraged to read arbitrary kernel memory. Decompression additionally reads through the wild context pointer.\nI:H - `lzo1x_1_compress()` writes up to LZO1X_MEM_COMPRESS (16KB) of hash-table state through the uncontrolled `ctx` pointer, an arbitrary kernel write, and `kvfree()` on a garbage pointer is an arbitrary-free primitive enabling heap grooming and control-flow hijack.\nA:H - Calling `kvfree()` on an uninitialized register value and then dereferencing a wild pointer as a scratch buffer reliably produces an oops or panic; on CFI-enabled builds the type-mismatched indirect call itself panics. The system is effectively unbootable or crashes on first compression."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:07:28.106Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.17.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.18"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}