CVE-2026-89720
CVE-2026-89720 is a security vulnerability. O3 Security confirms whether CVE-2026-89720 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
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…
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.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-89720 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89720 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-89720. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-89720 in your dependencies?
O3 detects CVE-2026-89720 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.