CVE-2026-89720ubifs: fix out-of-bounds read in signature length check
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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In the Linux kernel, the following vulnerability has been resolved: ubifs: fix out-of-bounds read in signature length check ubifs_sb_verify_signature() bounds the on-disk ubifs_sig_node->len field before handing the signature payload to verify_pkcs7_signature(), but the check has the wrong sign: if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) The signature bytes start sizeof(struct ubifs_sig_node) (UBIFS_SIG_NODE_SZ, 64 bytes) into the node, so the payload is at most snod->len - sizeof(struct ubifs_sig_node) bytes long. Adding the header size instead of subtracting it accepts a declared length up to 2 * UBIFS_SIG_NODE_SZ larger than the node actually holds -- past the end of c->sbuf, which is vmalloc(c->leb_size). verify_pkcs7_signature() -> pkcs7_parse_message() -> asn1_ber_decoder() is then handed that inflated length and reads beyond the allocation while walking the DER headers. The node length comes straight from the mounted image, so a crafted signed UBIFS image reaches this via ubifs_read_superblock() before the signature is cryptographically checked. snod->len is guaranteed to be >= UBIFS_SIG_NODE_SZ by the node scanner (c->ranges[UBIFS_SIG_NODE].min_len == UBIFS_SIG_NODE_SZ), so the corrected subtraction cannot underflow. Legitimately signed images are unaffected: a correct superblock never declares a signature longer than the node it is embedded in.
- CVSS
- 7.7 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Received
- Record last updated
- Oct 19, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 817aa094842dfc3a6b98c9582d4a647827f66201 before ab7405bd86331cc2dbc8201699d4adc33bea75e7; 817aa094842dfc3a6b98c9582d4a647827f66201 builds before 11abc34698cb3172badf8aa12e623f1bac98bbd8; 817aa094842dfc3a6b98c9582d4a647827f66201 builds before 8cc3da72cf57acb4b77442ea8cec48425dff7c06; 817aa094842dfc3a6b98c9582d4a647827f66201 builds before 37a9d25a563f5f9103282954ce573c4a61321e7c; from 817aa094842dfc3a6b98c9582d4a647827f66201 before f76b79d6e42af20682495bccd22f72c7164b0018; from 817aa094842dfc3a6b98c9582d4a647827f66201 before a1dc246f98bb94233effa4fa3ec7bf84700bb7d1; 817aa094842dfc3a6b98c9582d4a647827f66201 builds before 83e1aa9f5f906c9b1f4949d0521f0f950a159d96; 817aa094842dfc3a6b98c9582d4a647827f66201 builds before 95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf | CNA record |
References
- https://git.kernel.org/stable/c/ab7405bd86331cc2dbc8201699d4adc33bea75e7
- https://git.kernel.org/stable/c/11abc34698cb3172badf8aa12e623f1bac98bbd8
- https://git.kernel.org/stable/c/8cc3da72cf57acb4b77442ea8cec48425dff7c06
- https://git.kernel.org/stable/c/37a9d25a563f5f9103282954ce573c4a61321e7c
- https://git.kernel.org/stable/c/f76b79d6e42af20682495bccd22f72c7164b0018
- https://git.kernel.org/stable/c/a1dc246f98bb94233effa4fa3ec7bf84700bb7d1
- https://git.kernel.org/stable/c/83e1aa9f5f906c9b1f4949d0521f0f950a159d96
- https://git.kernel.org/stable/c/95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.