CVE-2026-6091: Partial-chain certificate verification may accept chains that terminate at a peer-supplied, untrusted intermed

Routine

MEDIUM 6.5UPGRADE

CVE-2026-6091 is a medium-severity flaw (CVSS 6.5) affecting wolfssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Partial-chain certificate verification may accept chains that terminate at a peer-supplied, untrusted intermediate certificate rather than a trusted anchor. An attacker could present a chain that ends at an intermediate they control and have it accepted as valid. This affects the OpenSSL compatibility certificate-path-building path (wolfSSL_X509_verify_cert / X509_STORE, OPENSSL_EXTRA) when the X509_V_FLAG_PARTIAL_CHAIN verify flag is enabled.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 91%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-06-25
Last modified	2026-06-26

Publisher (CNA): wolfSSL Inc. · Vendor: wolfssl

Last updated 2026-06-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-25 18:16 UTCPublished CVE record published
2026-06-26 16:50 UTCUpdated Record last modified

wolfssl wolfssl UPGRADE

Affected: >= 5.7.4 and < 5.9.2

Fixed in: 5.9.2

Safe to downgrade to: a release before 5.7.4

1. Check installed version

apt-cache policy wolfssl || rpm -q wolfssl || wolfssl --version

2. UPGRADE to 5.9.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade wolfssl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade wolfssl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.7.4 (Debian / Ubuntu)

apt-cache madison wolfssl sudo apt install wolfssl=<VERSION_BEFORE_5.7.4> sudo apt-mark hold wolfssl

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list wolfssl sudo dnf downgrade wolfssl-<VERSION_BEFORE_5.7.4> sudo dnf versionlock add wolfssl

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-6091?

wolfssl: upgrade to 5.9.2. Exact commands for each OS are on this page.

Is CVE-2026-6091 being exploited?

CVE-2026-6091 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-6091 affect?

CVE-2026-6091 affects wolfssl. Severity is medium (CVSS 6.5). Partial-chain certificate verification may accept chains that terminate at a peer-supplied, untrusted intermediate certificate rather than a trusted anchor. An attacker could present a chain that ends at an intermediate they control and hav

How urgent is CVE-2026-6091?

Priority 25/100. No elevated risk signals yet.

Software pages

OpenSSL vulnerabilities · wolfSSL vulnerabilities

Related CVEs

CVE-2026-55967 HIGH 7.5 UPGRADE AES-GCM encryption/decryption with extremely large cumulative single message sizes (>64 GiB) were not properly
CVE-2026-7532 HIGH 7.5 UPGRADE iPAddress name constraints bypass when WOLFSSL_IP_ALT_NAME is not defined
CVE-2026-6678 MEDIUM 5.3 UPGRADE Integer underflow in wc_PKCS7_DecryptOri when handling crafted Other Recipient Info, leading to incorrect leng
CVE-2026-6679 HIGH 7.5 UPGRADE A heap buffer overflow could occur in the DTLS 1.3 ACK serialization path before the connecting peer is authen
CVE-2026-6681 MEDIUM 5.3 UPGRADE The PKCS#7 decode path ignores the caller-supplied output buffer size (outputSz), allowing decoded content to

References

← Back to latest CVEs