{"id":"CVE-2026-62381","summary":"luci-lib-px5g 2040-bit Certificate Signing Heap Buffer Overflow","details":"luci-lib-px5g (LuCI) contains a heap-based buffer overflow in the native ASN.1 encoding routine asn1_add_obj (x509write.c) when signing a certificate with a 2040-bit RSA key. For a 255-byte signature, the BIT STRING allocation is computed from the DER length encoding of 255 bytes, but the payload written after prepending the unused-bits byte is 256 bytes, requiring one additional DER length octet. As a result the allocation is 259 bytes while the tag, length, unused-bits byte, and signature require 260 bytes, and the final memcpy writes one byte beyond the heap buffer. The overflow is reachable through the exported Lua interface via create_selfsigned(); whether it is remotely exploitable depends on the embedding application. The vulnerable code is present on the openwrt-18.06 through openwrt-25.12 release branches and is absent from master, where the luci-lib-px5g package has been removed rather than patched.","aliases":["GHSA-jgc3-4q3p-g6xh"],"modified":"2026-10-21T02:58:54.293170809Z","published":"2026-08-22T12:26:44.558Z","database_specific":{"cwe_ids":["CWE-122"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62381.json","cna_assigner":"VulnCheck"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62381.json"},{"type":"ADVISORY","url":"https://github.com/openwrt/luci/security/advisories/GHSA-jgc3-4q3p-g6xh"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-62381"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/luci-lib-px5g-2040-bit-certificate-signing-heap-buffer-overflow"},{"type":"PACKAGE","url":"https://github.com/openwrt/luci"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/openwrt/luci","events":[{"introduced":"0"},{"last_affected":"42d72f79cd8f057f241595abc761b39dab2d9f07"}],"database_specific":{"extracted_events":[{"range":[{"introduced":"0"},{"last_affected":"42d72f79cd8f057f241595abc761b39dab2d9f07"}],"source":"AFFECTED_FIELD","strategy":"StandardRange"}]}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-62381.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N"}]}