{"id":"CVE-2026-89720","title":"ubifs: fix out-of-bounds read in signature length check","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: fix out-of-bounds read in signature length check\n\nubifs_sb_verify_signature() bounds the on-disk ubifs_sig_node->len field\nbefore handing the signature payload t…","severity":"high","cvss":7.7,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","cvssSource":"cna","cwe":["CWE-125"],"vendor":"Linux","product":"Linux","affected":["Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < ab7405bd86331cc2dbc8201699d4adc33bea75e7","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 11abc34698cb3172badf8aa12e623f1bac98bbd8","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 8cc3da72cf57acb4b77442ea8cec48425dff7c06","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 37a9d25a563f5f9103282954ce573c4a61321e7c","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < f76b79d6e42af20682495bccd22f72c7164b0018","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < a1dc246f98bb94233effa4fa3ec7bf84700bb7d1","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 83e1aa9f5f906c9b1f4949d0521f0f950a159d96","Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf","Linux 5.3"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:51:33.033Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89720","references":[{"url":"https://git.kernel.org/stable/c/ab7405bd86331cc2dbc8201699d4adc33bea75e7"},{"url":"https://git.kernel.org/stable/c/11abc34698cb3172badf8aa12e623f1bac98bbd8"},{"url":"https://git.kernel.org/stable/c/8cc3da72cf57acb4b77442ea8cec48425dff7c06"},{"url":"https://git.kernel.org/stable/c/37a9d25a563f5f9103282954ce573c4a61321e7c"},{"url":"https://git.kernel.org/stable/c/f76b79d6e42af20682495bccd22f72c7164b0018"},{"url":"https://git.kernel.org/stable/c/a1dc246f98bb94233effa4fa3ec7bf84700bb7d1"},{"url":"https://git.kernel.org/stable/c/83e1aa9f5f906c9b1f4949d0521f0f950a159d96"},{"url":"https://git.kernel.org/stable/c/95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89720.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89720"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532147"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89720"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89720"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89720.mbox"}],"tags":["cve.org","csaf","vex","red-hat","score-dispute"],"epss":0.00185,"epssPercentile":0.08014,"scores":{"cna":7.7,"vendor":5.5},"ingestedAt":"2026-09-14T15:23:07.449Z","slug":"CVE-2026-89720","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nubifs: fix out-of-bounds read in signature length check\n\nubifs_sb_verify_signature() bounds the on-disk ubifs_sig_node->len field\nbefore handing the signature payload to verify_pkcs7_signature(), but the\ncheck has the wrong sign:\n\n\tif (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node))\n\nThe signature bytes start sizeof(struct ubifs_sig_node) (UBIFS_SIG_NODE_SZ,\n64 bytes) into the node, so the payload is at most\n\n\tsnod->len - sizeof(struct ubifs_sig_node)\n\nbytes long. Adding the header size instead of subtracting it accepts a\ndeclared length up to 2 * UBIFS_SIG_NODE_SZ larger than the node actually\nholds -- past the end of c->sbuf, which is vmalloc(c->leb_size).\nverify_pkcs7_signature() -> pkcs7_parse_message() -> asn1_ber_decoder()\nis then handed that inflated length and reads beyond the allocation while\nwalking the DER headers. The node length comes straight from the mounted\nimage, so a crafted signed UBIFS image reaches this via\nubifs_read_superblock() before the signature is cryptographically checked.\n\nsnod->len is guaranteed to be >= UBIFS_SIG_NODE_SZ by the node scanner\n(c->ranges[UBIFS_SIG_NODE].min_len == UBIFS_SIG_NODE_SZ), so the corrected\nsubtraction cannot underflow. Legitimately signed images are unaffected: a\ncorrect superblock never declares a signature longer than the node it is\nembedded in.\n\n## Affected\n\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < ab7405bd86331cc2dbc8201699d4adc33bea75e7`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 11abc34698cb3172badf8aa12e623f1bac98bbd8`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 8cc3da72cf57acb4b77442ea8cec48425dff7c06`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 37a9d25a563f5f9103282954ce573c4a61321e7c`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < f76b79d6e42af20682495bccd22f72c7164b0018`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < a1dc246f98bb94233effa4fa3ec7bf84700bb7d1`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 83e1aa9f5f906c9b1f4949d0521f0f950a159d96`\n- `Linux >= 817aa094842dfc3a6b98c9582d4a647827f66201 < 95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf`\n- `Linux 5.3`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89720.json)","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":42.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224600,"id":"CVE-2026-89720","ts":1792401429227,"field":"cvss","old":"5.5","new":"7.7"},{"seq":224599,"id":"CVE-2026-89720","ts":1792401429227,"field":"severity","old":"medium","new":"high"},{"seq":205516,"id":"CVE-2026-89720","ts":1789576723093,"field":"cvss","old":"7.7","new":"5.5"},{"seq":205515,"id":"CVE-2026-89720","ts":1789576723093,"field":"severity","old":"high","new":"medium"},{"seq":197698,"id":"CVE-2026-89720","ts":1789384318456,"field":"cvss","old":"4.7","new":"7.7"},{"seq":197697,"id":"CVE-2026-89720","ts":1789384318456,"field":"severity","old":"medium","new":"high"},{"seq":183339,"id":"CVE-2026-89720","ts":1789356674945,"field":"cvss","old":"7.7","new":"4.7"},{"seq":183338,"id":"CVE-2026-89720","ts":1789356674945,"field":"severity","old":"high","new":"medium"},{"seq":153606,"id":"CVE-2026-89720","ts":1789285351468,"field":"cvss","old":null,"new":"7.7"},{"seq":153605,"id":"CVE-2026-89720","ts":1789285351468,"field":"severity","old":"none","new":"high"},{"seq":147686,"id":"CVE-2026-89720","ts":1789270211881,"field":"cvss","old":null,"new":"4.7"},{"seq":147685,"id":"CVE-2026-89720","ts":1789270211881,"field":"severity","old":"none","new":"medium"},{"seq":109438,"id":"CVE-2026-89720","ts":1789183731915,"field":"cvss","old":null,"new":"4.7"},{"seq":109437,"id":"CVE-2026-89720","ts":1789183731915,"field":"severity","old":"none","new":"medium"}]}