CVE-2026-6681: PKCS#7 decode ignores caller output buffer size, writing past buffer bounds
Vulnerability summary
CVE-2026-6681 is a medium (CVSS 5.3) vulnerability in wolfssl. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 31.6% of scored vulnerabilities.
Not severe (CVSS 1, adjacent network); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Timeline
- 25-06-2026PublishedVulnerability first disclosed.
- 26-06-2026Last modifiedVulnerability information updated.
Description
The PKCS#7 decode path ignores the caller-supplied output buffer size (outputSz), allowing decoded content to be written past the bounds of the provided buffer. This affects wolfSSL 5.9.0 and earlier and was fixed in the 5.9.1 release.
CVSS metrics
7 scores · 5 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated1.0LowCVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/U:Clear
- NVDNIST1.0LowCVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Clear
- OSV · UbuntuEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- OSV · DebianEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- OSV · AlpineEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS trend
Probability
0.38%
Chance of exploitation in the next 30 days
Percentile
32%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.38% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-120Buffer Copy without Checking Size of InputThe product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
- CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.
Affected systems
Known conditions: adjacent network, low-privilege account, user interaction (CVSS vector). Other conditions: not stated in public data.
Alpine1 product
- wolfssl≥ 3.10.0, < 5.9.2-r0
Debian1 product
- wolfssl< 5.5.4-2+deb12u3 | < 5.7.2-0.1+deb13u2
Ubuntu1 product
- wolfsslAll versions (No fix recorded)
Wolfssl1 product
- wolfssl≥ 3.10.0, ≤ 5.9.0 | ≥ 3.10.0, < 5.9.1
4 vendors · 4 products
