ubifs: fix out-of-bounds read in signature length check

Description

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.

Timeline

Scores

EPSS (exploitation in 30 days)

0.18% · top 92% of all CVEs (11 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.7.

Affected products

• Linux · Linux

  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < ab7405bd86331cc2dbc8201699d4adc33bea75e7
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < 11abc34698cb3172badf8aa12e623f1bac98bbd8
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < 8cc3da72cf57acb4b77442ea8cec48425dff7c06
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < 37a9d25a563f5f9103282954ce573c4a61321e7c
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < f76b79d6e42af20682495bccd22f72c7164b0018
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < a1dc246f98bb94233effa4fa3ec7bf84700bb7d1
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < 83e1aa9f5f906c9b1f4949d0521f0f950a159d96
  • affected 817aa094842dfc3a6b98c9582d4a647827f66201 – < 95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf

• Linux · Linux

  • affected 5.3
  • unaffected < 5.3
  • unaffected 5.10.270 – ≤ 5.10.*
  • unaffected 5.15.221 – ≤ 5.15.*
  • unaffected 6.1.188 – ≤ 6.1.*
  • unaffected 6.6.157 – ≤ 6.6.*
  • unaffected 6.12.109 – ≤ 6.12.*
  • unaffected 6.18.50 – ≤ 6.18.*
  • unaffected 7.2.4 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-76632 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-89720](https://cveledger.app/badge/CVE-2026-89720.svg)](https://cveledger.app/cve/CVE-2026-89720)

Record last updated 19 Oct 2026, 08:51 UTC.