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CVE-2026-5188

Integer underflow in X.509 SAN parsing in wolfSSL

2.3 LowFix available

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
Low

Exploit likelihood

0.14%Up 0.1 points since Apr 10, 2026
90%50%10%1%

What each source reports

CVE List Score used 2.3

Integer underflow in X.509 SAN parsing in wolfSSL

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
CVE-2026-5188
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-191
Updated
2026-11-02
EUVDEUVD-2026-21290 2.3

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
EUVD-2026-21290
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-9qgc-pcpx-g38q 2.3

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN)...

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
GHSA-9qgc-pcpx-g38q
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/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:X
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Weakness
CWE-191
Updated
2026-11-02
NVD 2.3

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
CVE-2026-5188
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/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:X
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Weakness
CWE-191
Updated
2026-11-02
OSVALPINE-CVE-2026-5188 8.1

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
ALPINE-CVE-2026-5188
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Updated
2026-11-03
OSV 2.3

Integer underflow in X.509 SAN parsing in wolfSSL

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
CVE-2026-5188
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-191
Updated
2026-11-02
OSVDEBIAN-CVE-2026-5188 8.1

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
DEBIAN-CVE-2026-5188
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Updated
2026-11-02
OSVJLSEC-2026-715 2.3

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN)...

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
JLSEC-2026-715
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/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:X
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-5188 2.3

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Record
UBUNTU-CVE-2026-5188
CVSS 4.0
2.3 LowCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
wolfssl
Alpine:v3.23
 before 5.9.1-r0
5.9.1-r0
wolfssl
Alpine:v3.24
 before 5.9.1-r0
5.9.1-r0
wolfssl
Debian:12
 All versions, plus listed versions
5.5.4-25.5.4-2+deb12u15.5.4-2+deb12u25.5.4-2+deb12u35.5.4-2.1
Show 22 moreShow less
5.6.4-15.6.4-25.6.6-15.6.6-1.15.6.6-1.25.6.6-1.35.6.6-1.3~exp15.7.0-0.15.7.0-0.25.7.0-0.35.7.2-0.15.7.2-0.25.7.2-0.35.7.2-0.45.8.2-15.8.2-1.15.8.2-1.25.8.4-15.9.0-0.15.9.0-0.25.9.1-0.15.9.2-1
 None known
wolfssl
Debian:13
 All versions, plus listed versions
5.7.2-0.15.7.2-0.1+deb13u15.7.2-0.1+deb13u25.7.2-0.25.7.2-0.3
Show 9 moreShow less
5.7.2-0.45.8.2-15.8.2-1.15.8.2-1.25.8.4-15.9.0-0.15.9.0-0.25.9.1-0.15.9.2-1
 None known
wolfSSL_jll
Julia
 before 5.9.2+0
5.9.2+0
wolfssl
Ubuntu:16.04:LTS
 All versions, plus listed versions
3.4.8+dfsg-1
 None known
wolfssl
Ubuntu:18.04:LTS
 All versions, plus listed versions
3.10.2+dfsg-23.12.0+dfsg-13.12.2+dfsg-13.13.0+dfsg-1
 None known
wolfssl
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.1.0+dfsg-24.2.0+dfsg-14.2.0+dfsg-24.2.0+dfsg-34.3.0+dfsg-2
 None known
wolfssl
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.6.0-35.0.0-15.1.1-15.2.0-15.2.0-2
 None known
wolfssl
Ubuntu:24.04:LTS
 All versions, plus listed versions
5.5.4-25.5.4-2.15.6.4-25.6.6-1.25.6.6-1.35.6.6-1.3build1
 None known
wolfssl
Ubuntu:25.10
 All versions, plus listed versions
5.7.2-0.1
 None known
wolfssl
Ubuntu:26.10
 All versions, plus listed versions
5.9.1-0.15.9.2-1
 None known
wolfssl
Ubuntu:26.04:LTS
 All versions, plus listed versions
5.7.2-0.15.8.2-1.25.8.4-15.9.1-0.1
 None known

History

History
RecordedChangedSources
affected, aliases, referencesOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-5188 is a low vulnerability (CVSS 2.3) in Wolfssl, published April 10, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. Fixed in wolfssl 5.9.1-r0.

References

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