{"id":"CVE-2026-64089","state":"PUBLISHED","title":"batman-adv: tt: fix negative last_changeset_len","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbatman-adv: tt: fix negative last_changeset_len\n\nbatadv_piv_tt::last_changeset_len len was declared as s16, but the field is\nnever intended to hold a negative value. When a value greater than 32767 is\nassigned, it wraps to a negative signed integer.\n\nIn batadv_send_my_tt_response(), last_changeset_len is temporarily widened\nto s32. The incorrectly negative s16 value propagates into the s32, causing\nbatadv_tt_prepare_tvlv_local_data() to allocate a full sized buffer but\npopulates only a small portion of it with the collected changeset. All\nremaining bits are kept uninitialized.\n\nUsing an u16 avoids this type confusion and ensures that no (negative) sign\nextension is performed in batadv_send_my_tt_response().","publishedAt":"2026-07-19T15:39:58.729Z","updatedAt":"2026-08-05T12:39:06.132Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/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":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"6314089acf0ddf64376fdc0b1420695504c73f52","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"55dc41fe8821e9a849e147255ad572bc933a9d15","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"c424e8519ac78eac5d9f4eecf06208a0d619ec14","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"22d59c72f4a47ffec121d0610f70d0d70c3c11c8","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"eb235472b52ef36981c5aad330485eaf2382c53b","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"179eb62506a02d00370bd6478898cb632e10986c","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"d29abf70c665730e249d2ec8e1402095ae26bcee","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"fc92cdfcb295cefa4344d71a527d61b638b7bfc4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/batman-adv/types.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.1","versionType":"semver"},{"version":"5.10.258","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.209","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.175","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.142","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.92","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/batman-adv/types.h"]}],"references":["https://git.kernel.org/stable/c/6314089acf0ddf64376fdc0b1420695504c73f52","https://git.kernel.org/stable/c/55dc41fe8821e9a849e147255ad572bc933a9d15","https://git.kernel.org/stable/c/c424e8519ac78eac5d9f4eecf06208a0d619ec14","https://git.kernel.org/stable/c/22d59c72f4a47ffec121d0610f70d0d70c3c11c8","https://git.kernel.org/stable/c/eb235472b52ef36981c5aad330485eaf2382c53b","https://git.kernel.org/stable/c/179eb62506a02d00370bd6478898cb632e10986c","https://git.kernel.org/stable/c/d29abf70c665730e249d2ec8e1402095ae26bcee","https://git.kernel.org/stable/c/fc92cdfcb295cefa4344d71a527d61b638b7bfc4"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64089.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64089","state":"PUBLISHED","datePublished":"2026-07-19T15:39:58.729Z","dateUpdated":"2026-08-05T12:39:06.132Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.032Z"},"containers":{"cna":{"title":"batman-adv: tt: fix negative last_changeset_len","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbatman-adv: tt: fix negative last_changeset_len\n\nbatadv_piv_tt::last_changeset_len len was declared as s16, but the field is\nnever intended to hold a negative value. When a value greater than 32767 is\nassigned, it wraps to a negative signed integer.\n\nIn batadv_send_my_tt_response(), last_changeset_len is temporarily widened\nto s32. The incorrectly negative s16 value propagates into the s32, causing\nbatadv_tt_prepare_tvlv_local_data() to allocate a full sized buffer but\npopulates only a small portion of it with the collected changeset. All\nremaining bits are kept uninitialized.\n\nUsing an u16 avoids this type confusion and ensures that no (negative) sign\nextension is performed in batadv_send_my_tt_response()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"6314089acf0ddf64376fdc0b1420695504c73f52","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"55dc41fe8821e9a849e147255ad572bc933a9d15","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"c424e8519ac78eac5d9f4eecf06208a0d619ec14","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"22d59c72f4a47ffec121d0610f70d0d70c3c11c8","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"eb235472b52ef36981c5aad330485eaf2382c53b","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"179eb62506a02d00370bd6478898cb632e10986c","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"d29abf70c665730e249d2ec8e1402095ae26bcee","versionType":"git"},{"version":"a73105b8d4c765d9ebfb664d0a66802127d8e4c7","status":"affected","lessThan":"fc92cdfcb295cefa4344d71a527d61b638b7bfc4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/batman-adv/types.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.1","versionType":"semver"},{"version":"5.10.258","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.209","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.175","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.142","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.92","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/batman-adv/types.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/6314089acf0ddf64376fdc0b1420695504c73f52"},{"url":"https://git.kernel.org/stable/c/55dc41fe8821e9a849e147255ad572bc933a9d15"},{"url":"https://git.kernel.org/stable/c/c424e8519ac78eac5d9f4eecf06208a0d619ec14"},{"url":"https://git.kernel.org/stable/c/22d59c72f4a47ffec121d0610f70d0d70c3c11c8"},{"url":"https://git.kernel.org/stable/c/eb235472b52ef36981c5aad330485eaf2382c53b"},{"url":"https://git.kernel.org/stable/c/179eb62506a02d00370bd6478898cb632e10986c"},{"url":"https://git.kernel.org/stable/c/d29abf70c665730e249d2ec8e1402095ae26bcee"},{"url":"https://git.kernel.org/stable/c/fc92cdfcb295cefa4344d71a527d61b638b7bfc4"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The bug is reached when a remote mesh peer's TT_REQUEST is processed via batman-adv's network receive path (batadv_recv_unicast_tvlv), which handles ETH_P_BATMAN packets from network-facing mesh interfaces without requiring local access.\nAC:L - Once the victim has a wrapped last_changeset_len (achievable on high-MTU mesh nodes with >2730 TT changes), the attacker reliably triggers the bug by sending a crafted TT_REQUEST with matching ttvn and without BATADV_TT_FULL_TABLE; no race or victim-dependent timing is required.\nPR:N - Exploitation requires only the ability to send batman-adv protocol packets as a mesh peer; no account, credentials, or elevated privileges on the victim system are needed, and TT_REQUEST handling has no authentication gate beyond being a known originator in the mesh.\nUI:N - The victim administrator or end user need take no action during exploitation; the attacker sends a TT_REQUEST and the kernel processes it automatically in response to received mesh traffic.\nS:U - The vulnerability corrupts kernel heap memory and leaks kernel data within the kernel's own security boundary; it does not cross into another security authority such as a VM guest-to-host or sandbox escape.\nC:H - Sign-extended negative last_changeset_len causes memcpy() to read far beyond the small last_changeset buffer (OOB heap read), and the oversized kmalloc response buffer retains uninitialized kernel memory that is copied into the TT_RESPONSE sent back to the attacker.\nI:H - The same memcpy() with a sign-extended negative length writes far beyond the allocated tt_change region in the kmalloc buffer, causing out-of-bounds heap corruption that can be leveraged for arbitrary kernel writes or control-flow hijacking.\nA:H - The massive out-of-bounds memcpy() from a wrapped s16 length will cause kernel memory corruption, oops, or panic, and even partial execution leaks uninitialized data before potential crash."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:39:06.132Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"5.10.258"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"5.15.209"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.1.175"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.6.142"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.12.92"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}