CoreCVE
Back

HIGH

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

Published Sep 11, 2026

Description

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.

Affected products

Remediation

No remediation recorded yet.

Metrics

Weaknesses (1)

CWE-125

Out-of-bounds Read

References (13)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner Linux
Published Sep 11, 2026
Updated Sep 14, 2026
Reserved Sep 11, 2026
Link CVE-2026-89720
CISA Vulnrichment
Updated n/a
NVD
Status Received
Modified Sep 14, 2026
Link CVE-2026-89720
Red Hat
Severity Moderate
Public date Sep 11, 2026
Links CVE-2026-89720 - Bugzilla