CVE-2026-62381
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.
- CVSS 4.0
- 6.9
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 - CVSS 3.1
- 6.6
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H - EPSS
- 0.1% chance of exploitation in the next 30 days; higher than 1% of CVEs (scores of 2026-10-25)
- CWE
- CWE-122
- Published
- Modified
- Record from
- the NVD, synced