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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89720
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:20:00 UTC
Updated2026-09-11 20:20:00 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 817aa094842dfc3a6b98c9582d4a647827f66201 f76b79d6e42af20682495bccd22f72c7164b0018 git Not specified
CNA Linux Linux affected 817aa094842dfc3a6b98c9582d4a647827f66201 a1dc246f98bb94233effa4fa3ec7bf84700bb7d1 git Not specified
CNA Linux Linux affected 817aa094842dfc3a6b98c9582d4a647827f66201 83e1aa9f5f906c9b1f4949d0521f0f950a159d96 git Not specified
CNA Linux Linux affected 817aa094842dfc3a6b98c9582d4a647827f66201 95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf git Not specified
CNA Linux Linux affected 5.3 Not specified
CNA Linux Linux unaffected 5.3 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/83e1aa9f5f906c9b1f4949d0521f0f950a159d96 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a1dc246f98bb94233effa4fa3ec7bf84700bb7d1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f76b79d6e42af20682495bccd22f72c7164b0018 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/95d27c1708bb6e8823c8e7c623f9abc2a91bf4bf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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