Buffer overflow in Wolfssl
CVE-2026-5187
Two potential heap out-of-bounds write locations existed in DecodeObjectId() in wolfcrypt/src/asn.c. First, a bounds check only validates one available slot before writing two OID arc values (out[0] and out[1]), enabling a 2-byte out-of-bounds write when outSz equals 1. Second, multiple callers pass sizeof(decOid) (64 bytes on 64-bit platforms) instead of the element count MAX_OID_SZ (32), causing the function to accept crafted OIDs with 33 or more arcs that write past the end of the allocated buffer.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (39.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Wolfssl — versions 0
Weakness classification (CWE)
References
- github.com/wolfSSL/wolfssl (Product)
Frequently asked questions
- What is CVE-2026-5187?
- CVE-2026-5187 is a critical-severity vulnerability in Wolfssl, classified under Heap-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-04-09.
- How severe is CVE-2026-5187?
- Critical severity. CVSS v3 base score is 9.8 out of 10.