{"id":"CVE-2024-26994","state":"PUBLISHED","title":"speakup: Avoid crash on very long word","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nspeakup: Avoid crash on very long word\n\nIn case a console is set up really large and contains a really long word\n(> 256 characters), we have to stop before the length of the word buffer.","publishedAt":"2024-05-01T05:28:07.350Z","updatedAt":"2026-08-05T11:28:53.774Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux 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- The overflow is reached only through the speakup console screen-reader command path (`keyboard_notifier_call` → `speakup_key` → `do_spkup` → `get_word`) combined with `VT_RESIZE`/`PIO_UNIMAP`/`KDFONTOP` ioctls on the attacker's own virtual console, all of which require a local session on the machine. There is no network or remote protocol handler involved, but console/VT access is standard local access rather than physical device attachment.\nAC:L - Every precondition is under the attacker's control: `vt_ioctl()` grants `perm=1` to the tty owner, so an unprivileged console user can `VT_RESIZE` the console past 257 columns (up to `VC_MAXCOL`=32767 outright when the VC is bound to dummycon, which has no `con_resize` clamp, or via a narrow `KDFONTOP` font under fbcon), then print a >256-character word and press the say-word key. No race, no memory-layout luck, and on 4K framebuffer consoles the stock 8x16 font already yields 480 columns by default.\nPR:L - The attacker needs an ordinary unprivileged local account owning a virtual console — `current->signal->tty == tty` alone satisfies the VT ioctl permission check, so no CAP_SYS_TTY_CONFIG or root is required, and `do_spkup()` performs no capability check before invoking `get_word()`.\nUI:N - The attacker performs every step themselves — resizing their own VT, loading the unimap, painting the long word, and issuing the speakup say-word/spell-word command; no separate victim needs to be induced into any action.\nS:U - The out-of-bounds write corrupts kernel `.bss` belonging to the same kernel security authority that contains the vulnerable code; no VM, hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - The linear overflow lands on `spk_characters[256]`, a pointer array immediately following `buf` in `.bss`, whose entries are dereferenced and printed via `synth_printf(\"%s\", cp)` into the synth buffer that userspace reads from `/dev/softsynth` — giving an arbitrary kernel-memory read primitive disclosed to the attacker, well beyond a bounded leak.\nI:H - This is an out-of-bounds write of fully attacker-chosen 16-bit values (sourced from an attacker-loaded `inverse_trans_unicode` table) with attacker-chosen length, overwriting adjacent `.bss` pointer arrays such as `spk_our_keys[]` and `speakup_console[]`, the latter being dereferenced for writes (`speakup_console[vc_num]->ht.highbuf[bi][hi] = ic[i]`) — an arbitrary-write and control-flow-influence primitive.\nA:H - Even without careful exploitation, smashing kilobytes of `.bss` past `buf[256]` corrupts live pointer arrays that speakup dereferences on the next key event, producing an immediate kernel oops/panic — the crash the commit title explicitly refers to."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T11:28:53.774Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"4.19.313"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"5.4.275"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"5.10.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"5.15.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"6.1.88"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"6.6.29"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"6.8.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.37","versionEndExcluding":"6.9"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":5.9,"attackVector":"LOCAL","baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L","integrityImpact":"LOW","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"LOW","privilegesRequired":"NONE","confidentialityImpact":"LOW"}},{"other":{"type":"ssvc","content":{"timestamp":"2024-07-17T14:52:12.815212Z","id":"CVE-2024-26994","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"problemTypes":[{"descriptions":[{"type":"CWE","lang":"en","description":"CWE-noinfo Not enough information"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-11-04T16:48:53.206Z"}},{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/756c5cb7c09e537b87b5d3acafcb101b2ccf394f","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/8f6b62125befe1675446923e4171eac2c012959c","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/6401038acfa24cba9c28cce410b7505efadd0222","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/0d130158db29f5e0b3893154908cf618896450a8","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/89af25bd4b4bf6a71295f07e07a8ae7dc03c6595","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/8defb1d22ba0395b81feb963b96e252b097ba76f","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/0efb15c14c493263cb3a5f65f5ddfd4603d19a76","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/c8d2f34ea96ea3bce6ba2535f867f0d4ee3b22e1","tags":["x_transferred"]},{"url":"https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html","tags":["x_transferred"]},{"url":"https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html","tags":["x_transferred"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DAMSOZXJEPUOXW33WZYWCVAY7Z5S7OOY/"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4EZ6PJW7VOZ224TD7N4JZNU6KV32ZJ53/"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GCBZZEC7L7KTWWAS2NLJK6SO3IZIL4WW/"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2025-11-04T17:15:52.431Z"}}]}}}