CVE-2026-62381 luci-lib-px5g 2040-bit Certificate Signing Heap Buffer Overflow
Heap buffer overflow in OpenWrt LuCI certificate signing allows potential code execution or denial of service via crafted RSA keys.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-62381?
CVE-2026-62381 is a medium-severity memory corruption vulnerability in openwrt luci, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-122
Which versions are affected by CVE-2026-62381?
How do I fix CVE-2026-62381?
No fix has been published for CVE-2026-62381 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-62381 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62381 exists.
Sources
Also known as GHSA-g4fj-xr23-w9hm, GHSA-jgc3-4q3p-g6xh.